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ILLUSTRATED SOURCEBOOK
ROBERT O. PARMLEY, P.E. Editor-in-Chief
McGraw-Hil NewM Ye oxrkcio C h c i a g oMalinSanNeF rancD sico LS sibao nJuaLnondon M addri C t y i w e h l i n S e o u l Snigapore Sydney Torono t Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l
Cataloging-in-Publication Data is on file with the Library of Congress.
Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Printed in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a data base or retrieval system, without the prior written permission of the publisher. 1 2 3 4 5 6 7 8 9 0 PBT/PBT 0 1 0 9 8 7 6 5 4 ISBN 0-07-143687-1
The sponsoring editor for this book was Kenneth P. McCombs and the production supervisor was Famela A. Pelton. The art director for the cover was Anthony Landi. Text Design by Wayne C. Parmley.
Printed and bound by Phoenix Book Tech. This book was printed on acid-free paper.
McGraw-Hill books are available at special quantity discounts to use as premiums and sales promotions, or for use in corporate training programs. For more information, please write to the Director of Special Sales, Professional Publishing, McGraw-Hill, Two Penn Plaza, New York, NY 10121-2298. Or contact your local bookstore. Information contained in this work has been obtained by The McGrawHill Companies, Inc. ("McGraw-Hill") from sources believed to be reliable. However, neither McGraw-Hill nor its editor in chief and authors guarantees the accuracy or completeness of any information published herein and neither McGraw-Hill nor its editor in chief and authors shall be responsible for any errors, omissions, or damages arising out of use of this information. This work is published with the understanding that McGraw-Hill and its editor in chief and authors are supplying information but are not attempting to render engineering or other professional services. If such services are required, the assistance of an appropriate professional should be sought.
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DEDICATED TO:
Regin & Spencer
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
P
Co py rig hte dM ate ria l
PREFACE
reservation of information, especially technical data, is essential for continued progress of any discipline of technology. Without the knowledge of basic elements, engineers, designers, craftsmen, and technicians are handicapped. In some cases, they would literally have to "reinvent the wheel"; thus wasting valuable time, resources and energy that could and should be spent on developing new designs.
We are told by respected archaeological experts that the pyramids of ancient Egypt and prehistoric South America were built without the use of pulleys and gears; both indispensable mechanical components since early Greek and Roman times. However, these magnificent structures were constructed, but apparently no recorded information exists describing their construction methods or erection tools they employed. Perhaps some unknown component, device, or mechanism was used by those ancient builders that remains unknown even to this day. Basic or standard designs are invaluable and often stimulate the creative process, which can lead to new components and mechanisms. But if they are not properly recorded and available for future review, those ideas can easily become lost. Fortunately, modern engineering literature has faithfully published handbooks, manuals and codes describing most standard designs. However, innovative devices and unusual component applications often escape a permanent place in technical literature. A classic example of this is the two-page illustrated design files featured in Product Engineering magazine. This bi-weekly publication, over the decades, contained thousands of innovative mechanical designs and applications. Unfortunately, this magazine ceased publication in the early 1970s, but some of the original articles were reprinted in Greenwood's books in the late 1950s and 1960s. Chironis' Mechanisms & Mechanical Devices Sourcebook and the recently published book entitled, Illustrated Sourcebook of Mechanical Components, the latter of which I had the honor to serve as Editor-in-Chief, also contained many selections from Product Engineering. Other technical magazines periodically include novel mechanical designs, as do various technical reports from professional societies. Too many of these articles and their innovative designs fade into obscurity. With the foregoing discussion in mind, it was proposed to produce a practical sourcebook of selected innovative material that machine designers could use as a reference. Therefore, this sourcebook is a modified and condensed version of the massive Illustrated Sourcebook of Mechanical Components with the emphasis on machine devices and unusual applications of components. Significant data was culled from that book and rearranged to fit into a new format. Additional material was obtained from other sources and blended into the manuscript to round out the presentation.
Copyright © 2005 by The McGraw-Hill Companies
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The reader will notice a wide range of drawing styles and techniques throughout the pages of this sourcebook. This material was prepared over many decades and the sources were very broad. It is the opinion of the Editor in Chief that the range of drafting modes adds authentically and character to the collection of devices and components. As always, a sourcebook of this kind draws on the talents, skills and knowledge of many individuals, organizations, consulting firms, publications, and technical societies. This effort is no exception. The sources, where known, have been faithfully recorded on the appropriate pages throughout the sourcebook. We thank them all. My son, Wayne, has again served as the graphic designer for this (our 6th) book. As always, his skills and professionalism have been top quality. In summary, it is hoped that this illustrated sourcebook will continue the tradition of its predecessors. Preservation and dissemination of this type of material is a professional obligation and should not be taken lightly. We trust that we have been true to that mission.
ROBERT O. PARMLEY, P.E.
Ladysmith, Wisconsin May 2004
Copyright © 2005 by The McGraw-Hill Companies
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
A
Co py rig hte dM ate ria l
INTRODUCTION
s previously stated in the Preface, the major portion of the material contained throughout this sourcebook has been culled from over five decades of technical publications. Thus, the reader will certainly notice the wide range of drafting techniques and printing styles. Because these differences do not affect the technical data, we have opted to let these variations stand, as originally printed, and believe they reveal a historical flavor to the overall presentation. Before the reader or user of the sourcebook commences to explore the pages, it should be stated that both the cross-referenced Index and Table of Contents (located at the opening of each section) were included to assist in finding specific items. This format has been timetested and insures user-friendliness. The sections of this sourcebook have been arranged into three general categories. They are: assemblies, power transmission and individual components. The first five sections (1 thru 5) are devoted to innovative mechanisms, creative assemblies, linkages, connections and related locking devices. The end product is the final assembly of various mechanical components into a mechanism, device, machine or system that performs a desired function. The next five sections (6 thru 10) illustrate mechanical power transmission; i.e., gears, gearing, clutches, chains, sprockets, ratchets, belts, belting, shafts and couplings. These sections include some of the essential mechanical combinations used in transporting power from its source to other locations. Some materials are basic while other data illustrates some novel designs. The third and concluding category is devoted to individual mechanical components. Sections 11 thru 20 depict some universal and innovative uses of standard mechanical components. These single components are the building blocks of mechanical mechanisms and assemblies. In every machine or mechanism, each component must be properly selected and precisely arranged in a predetermined position to result in a successfully functioning unit or device. As each assembly is connected to larger and more complex machines, the individual components become less noticeable, until the system fails. Then the component that malfunctioned becomes the focus of attention. Therefore, the designer must always bear in mind that every element of a machine or mechanism is extremely important. This sourcebook is not a textbook or standard handbook of machine design. Rather, it is a creative reference for designers of machine devices. The material contained herein is an illustrated collection of unique designs and novel applications extracted from hard-to-locate technical journals, out-of-print publications and private consultants whose specialized topics limited their dissemination to the general engineering community. Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l
Good design and creative innovations rarely are spontaneous. They are usually developed over time and generated from previous developments. Therefore, it is the core purpose of this sourcebook to provide the reader with a broad based assortment of unique designs and unusual component applications. Hopefully, these illustrations will inspire the readers' creative thought process and ultimately produce solutions to their respective design problems. It is the professional opinion of the Editor in Chief that to develop into a good designer of machine devices one must have access to a broad resource of mechanical data. This sourcebook aims to be a key element in the designer's library. From quick surveys to full-blown systematic searches of the material contained within these pages should inspire the user to develop innovative devices and cost-effective solutions to various design challenges. The hundreds of illustrations displayed on the following pages were developed by a long list of engineers, designers, inventors, technicians, and artisans over many decades. Consult these drawings and let their practical ideas speak to you. Let the collective ideas rearrange themselves into new and innovative designs. This in itself will honor those individuals who took the time to faithfully record the original material and thereby preserve their ideas and concepts.
ROBERT O. PARMLEY, RE. Editor in Chief
Copyright © 2005 by The McGraw-Hill Companies
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Contents
ix
Introduction .................................................................................................................................
xi
Section 1.
Co py rig hte dM ate ria l
Preface .......................................................................................................................................
Ingenious Mechanisms .......................................................................................
1-1
1.1
Modified Geneva Drives and Special Mechanisms ...........................................................
1-2
1.2
Overriding Spring Mechanisms for Low-torque Drives ......................................................
1-4
1.3
10 Ways to Amplify Mechanical Movements .....................................................................
1-6
1.4
10 Ways to Amplify Mechanical Action .............................................................................
1-8
1.5
How to Damp Axial and Rotational Motion ........................................................................
1-10
1.6
Make Diaphragms Work for You .......................................................................................
1-12
1.7
4 Ways to Eliminate Backlash ...........................................................................................
1-14
1.8
4 More Ways to Prevent Backlash ....................................................................................
1-16
1.9
Limit-switch Backlash ........................................................................................................
1-18
Creative Assemblies ...........................................................................................
2-1
2.1
Rotary Piston Engine .........................................................................................................
2-2
2.2
Milk Transfer System .........................................................................................................
2-3
2.3
Hydraulic Motor .................................................................................................................
2-4
2.4
Slash Errors with Sensitive Balance ..................................................................................
2-5
2.5
Control-locked Thwart Vibration and Shock ......................................................................
2-6
2.6
1-way Output from Speed Reducers .................................................................................
2-8
2.7
Torque-limiters Protect Light-duty Drives ..........................................................................
2-10
2.8
6 Ways to Prevent Overloading .........................................................................................
2-12
2.9
7 More Ways to Prevent Overloading ...............................................................................
2-14
2.10
7 Ways to Limit Shaft Rotation ..........................................................................................
2-16
2.11
Devices for Indexing or Holding Mechanical Movements ..................................................
2-18
2.12
Saw-matic Mechanism ......................................................................................................
2-19
2.13
Piping Assembly for Sewage Lift Station Control Vault .....................................................
2-20
2.14
Water Bike .........................................................................................................................
2-21
Linkages ..............................................................................................................
3-1
3.1
8 Basic Push-pull Linkages ...............................................................................................
3-2
3.2
5 Linkages for Straight-line Motion ....................................................................................
3-4
3.3
10 Ways to Change Straight-line Direction .......................................................................
3-6
3.4
9 More Ways to Change Straight-line Direction ................................................................
3-8
Section 2.
Section 3.
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vii
Contents 3.5
Linkage for Accelerating and Decelerating Linear Strokes ...............................................
3-10
3.6
Linkages for Multiplying Short Motions ..............................................................................
3-12
3.7
Seven Popular Types of Three-dimensional Drives ..........................................................
3-14
3.8
Power Thrust Linkages and Their Applications .................................................................
3-18
3.9
Toggle Linkage Applications in Different Mechanisms ......................................................
3-20
3.10
Four-bar Linkages and Typical Industrial Applications .....................................................
3-22
Connections ........................................................................................................
4-1
4.1
14 Ways to Fasten Hubs to Shafts ....................................................................................
4-2
4.2
Attaching Hubless Gears to Shafts ...................................................................................
4-4
4.3
10 Different Types of Splined Connections .......................................................................
4-6
4.4
Alternates for Doweled Fasteners .....................................................................................
4-8
4.5
6 More Alternates for Doweled Fastenings .......................................................................
4-10
4.6
29 Ways to Fasten Springs ...............................................................................................
4-12
4.7
20 Tamper-proof Fasteners ...............................................................................................
4-16
4.8
Lanced Metal Eliminates Separate Fasteners ...................................................................
4-18
4.9
Joining Circular Parts without Fasteners ...........................................................................
4-20
Locking Devices & Methods ..............................................................................
5-1
5.1
Friction Clamping Devices .................................................................................................
5-2
5.2
Retaining and Locking Detents .........................................................................................
5-4
5.3
How Spring Clamps Hold Workpieces ..............................................................................
5-6
5.4
Holding Fixture for Workpiece ...........................................................................................
5-8
5.5
15 Ways to Fasten Gears to Shafts ..................................................................................
5-9
5.6
8 Control Mountings ..........................................................................................................
5-14
5.7
8 Interlocking Sheetmetal Fasteners .................................................................................
5-16
5.8
Fastening Sheet-metal Parts by Tongues, Snaps, or Clinching ........................................
5-18
5.9
Snap Fasteners for Polyethylene ......................................................................................
5-20
5.10
Snap Fasteners for Polystyrene ........................................................................................
5-22
Gears & Gearing ..................................................................................................
6-1
6.1
Nomenclature of Gears .....................................................................................................
6-2
6.2
Graphical Representation of Gear Dimensions .................................................................
6-4
6.3
Worksheet Streamlines Bevel-gear Calculations ..............................................................
6-6
6.4
Alignment Chart for Face Gears ........................................................................................
6-8
6.5
Power Capacity of Spur Gears ..........................................................................................
6-10
6.6
Linear to Angular Conversion of Gear-tooth Index Error ...................................................
6-13
6.7
Checklist for Planetary-gear Sets ......................................................................................
6-14
6.8
Epicyclic Gear Trains ........................................................................................................
6-16
6.9
Cycloid Gear Mechanisms ................................................................................................
6-18
6.10
Cardan-gear Mechanisms .................................................................................................
6-25
6.11
Typical Methods of Providing Lubrication for Gear Systems .............................................
6-27
Section 4.
Section 5.
Section 6.
Co py rig hte dM ate ria l
viii
This page has been reformatted by Knovel to provide easier navigation. Copyright © 2005 by The McGraw-Hill Companies
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Contents Clutches ...............................................................................................................
7-1
7.1
Basic Types of Mechanical Clutches .................................................................................
7-2
7.2
Construction Details of Overriding Clutches ......................................................................
7-4
7.3
10 Ways to Apply Overrunning Clutches ...........................................................................
7-6
7.4
Low-cost Designs for Overrunning Clutches .....................................................................
7-8
7.5
Small Mechanical Clutches for Precise Service ................................................................
7-10
7.6
Centrifugal Clutches ..........................................................................................................
7-12
7.7
Serrated Clutches and Detents .........................................................................................
7-16
7.8
Spring Bands Grip Tightly to Drive Overrunning Clutch ....................................................
7-18
7.9
Accurate Solution for Disk-clutch Torque Capacity ...........................................................
7-19
7.10
Spring-loaded Pins Aid Sprags in One-way Clutch ...........................................................
7-20
7.11
Rolling-type Clutch ............................................................................................................
7-20
Chains, Sprockets & Ratchets ...........................................................................
8-1
8.1
History of Chains ...............................................................................................................
8-2
8.2
Ingenious Jobs for Roller Chain ........................................................................................
8-4
8.3
Bead Chains for Light Service ...........................................................................................
8-8
8.4
Methods for Reducing Pulsations in Chain Drives ............................................................
8-10
8.5
Lubrication of Roller Chains ..............................................................................................
8-12
8.6
Sheet Metal Gears, Sprockets, Worms & Ratchets ..........................................................
8-14
8.7
Ratchet Layout Analyzed ..................................................................................................
8-16
8.8
No Teeth Ratchets ............................................................................................................
8-18
8.9
One-way Drive Chain Solves Problem of Sprocket Skip ...................................................
8-20
Belts & Belting ....................................................................................................
9-1
9.1
Ten Types of Belt Drives ...................................................................................................
9-2
9.2
Find the Length of Open and Closed Belts .......................................................................
9-4
9.3
Getting in Step with Hybrid Belts .......................................................................................
9-6
9.4
Equations for Computing Creep in Belt Drives ..................................................................
9-10
9.5
Mechanisms for Adjusting Tension of Belt Drives .............................................................
9-14
9.6
Leather Belts-hp Loss and Speeds ...................................................................................
9-16
Section 10. Shafts & Couplings .............................................................................................
10-1
Section 8.
Section 9.
Co py rig hte dM ate ria l
Section 7.
ix
10.1
Overview of Shafts & Couplings ........................................................................................
10-2
10.2
Critical Speeds of End Supported Bare Shafts .................................................................
10-5
10.3
Shaft Torque: Charts Find Equivalent Sections ................................................................
10-6
10.4
Novel Linkage for Coupling Offset Shafts .........................................................................
10-8
10.5
Coupling of Parallel Shafts ................................................................................................ 10-10
10.6
Low-cost Methods of Coupling Small Diameter Shafts ..................................................... 10-12
10.7
Typical Methods of Coupling Rotating Shafts I ................................................................. 10-14
10.8
Typical Methods of Coupling Rotating Shafts II ................................................................ 10-16
10.9
Typical Designs of Flexible Couplings I ............................................................................. 10-18 This page has been reformatted by Knovel to provide easier navigation. Copyright © 2005 by The McGraw-Hill Companies
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x
Contents 10.10
Typical Designs of Flexible Couplings II ............................................................................ 10-20
10.11
Typical Designs of Flexible Couplings III ........................................................................... 10-22
10.12
Ten Universal Shaft Couplings .......................................................................................... 10-24
10.13
Novel Coupling Shifts Shafts ............................................................................................. 10-26
Section 11. Threaded Components .......................................................................................
11-1
Getting the Most from Screws ...........................................................................................
11-2
11.2
20 Dynamic Applications for Screw Threads .....................................................................
11-4
11.3
16 Ways to Align Sheets and Plates with One Screw .......................................................
11-8
11.4
Various Methods of Locking Threaded Members .............................................................. 11-10
11.5
How to Provide for Backlash in Threaded Parts ................................................................ 11-12
11.6
7 Special Screw Arrangements ......................................................................................... 11-14
11.7
World of Self-locking Screws ............................................................................................. 11-16
Co py rig hte dM ate ria l
11.1
Section 12. Pins ......................................................................................................................
12-1
12.1
Slotted Spring Pins Find Many Jobs .................................................................................
12-2
12.2
8 Unusual Jobs for Spring Pins .........................................................................................
12-4
12.3
8 Electrical Jobs for Spring Pins ........................................................................................
12-6
12.4
8 More Spring Pin Applications .........................................................................................
12-8
12.5
Uses of Split Pins .............................................................................................................. 12-10
12.6
Design Around Spiral Wrapped Pins ................................................................................. 12-12
12.7
A Penny-wise Connector: the Cotter Pin ........................................................................... 12-14
12.8
Standards of Slotted-type Spring Pins .............................................................................. 12-16
12.9
Standards of Coiled-type Spring Pins ............................................................................... 12-17
12.10
Standards of Grooved Pins ............................................................................................... 12-18
12.11
Standards of Round-head Grooved Drive Studs ............................................................... 12-19
12.12
Standards of Grooved T-head Cotter Pins ........................................................................ 12-20
12.13
Standards of Cotter Pins ................................................................................................... 12-21
12.14
Pin and Shaft of Equal Strength ........................................................................................ 12-22
Section 13. Springs .................................................................................................................
13-1
13.1
12 Ways to Put Springs to Work .......................................................................................
13-2
13.2
Multiple Uses of Coil Springs ............................................................................................
13-4
13.3
Control Depth Primer Tool Employs Coil Springs .............................................................
13-6
13.4
One Spring Returns the Hand Lever .................................................................................
13-8
13.5
6 More One Spring Lever Return Designs ........................................................................ 13-10
13.6
How to Stiffen Bellows with Springs .................................................................................. 13-12
13.7
Springs: How to Design for Variable Rate ......................................................................... 13-14
13.8
Adjustable Extension Springs ............................................................................................ 13-16
13.9
Compression Spring Adjustment Methods I ...................................................................... 13-18
13.10
Compression Spring Adjustment Methods II ..................................................................... 13-20
13.11
Flat Springs in Mechanisms .............................................................................................. 13-22 This page has been reformatted by Knovel to provide easier navigation. Copyright © 2005 by The McGraw-Hill Companies
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Contents
xi
13.12
Flat Springs Find More Work ............................................................................................. 13-24
13.13
Pneumatic Spring Reinforcement ...................................................................................... 13-26
Section 14. Cams ....................................................................................................................
14-1
Generating Cam Curves ....................................................................................................
14-2
14.2
Cams and Gears Team Up in Programmed Motion ..........................................................
14-9
14.3
Spherical Cams: Linking Up Shafts ................................................................................... 14-11
14.4
Modifications and Uses for Basic Types of Cams ............................................................. 14-14
14.5
Nomogram for Parabolic Cam with Radically Moving Follower ......................................... 14-16
Co py rig hte dM ate ria l
14.1
Section 15. Grommets, Spacers & Inserts ............................................................................
15-1
15.1
A Fresh Look at Rubber Grommets ..................................................................................
15-2
15.2
These Spacers Are Adjustable ..........................................................................................
15-4
15.3
Odd Jobs for Rubber Mushroom Bumpers ........................................................................
15-6
15.4
Spacers Used in Jigs & Fixtures .......................................................................................
15-8
15.5
Flanged Inserts Stabilize Multi-stroke Reloading Press ....................................................
15-9
15.6
Metal Inserts for Plastic Parts ............................................................................................ 15-10
15.7
How to Select Threaded Inserts ........................................................................................ 15-12
15.8
Applications of Helical Wire Inserts ................................................................................... 15-15
Section 16. Washers ...............................................................................................................
16-1
16.1
Ideas for Flat Washers ......................................................................................................
16-2
16.2
Versatile Flat Washers ......................................................................................................
16-4
16.3
Jobs for Flat Rubber Washers ...........................................................................................
16-6
16.4
Take Another Look at Serrated Washers ..........................................................................
16-8
16.5
Dished Washers Are Versatile Components ..................................................................... 16-10
16.6
Design Problems Solved with Belleville Spring Washers .................................................. 16-12
16.7
Creative Ideas for Cupped Washers ................................................................................. 16-14
16.8
SEM Applications .............................................................................................................. 16-16
16.9
SEM Standards Tables ..................................................................................................... 16-17
Section 17. O-rings .................................................................................................................
17-1
17.1
8 Unusual Applications for O-rings ....................................................................................
17-2
17.2
16 Unusual Applications for the O-ring ..............................................................................
17-4
17.3
Look at O-rings Differently .................................................................................................
17-6
17.4
O-rings Solve Design Problems I ......................................................................................
17-8
17.5
O-rings Solve Design Problems II ..................................................................................... 17-10
17.6
7 More Applications for O-rings ......................................................................................... 17-12
17.7
Design Recommendations for O-ring Seals ...................................................................... 17-14
17.8
O-ring Seals for Pump Valves ........................................................................................... 17-16
Section 18. Retaining Rings ................................................................................................... 18.1
Comparisons of Retaining Rings versus Typical Fasteners .............................................. This page has been reformatted by Knovel to provide easier navigation. Copyright © 2005 by The McGraw-Hill Companies
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18-1 18-2
xii
Contents 18.2
Retaining Rings Aid Assembly, I .......................................................................................
18-4
18.3
Retaining Rings Aid Assembly, Il ......................................................................................
18-6
18.4
Coupling Shafts with Retaining Rings ...............................................................................
18-8
18.5
The Versatile Retaining Ring ............................................................................................. 18-12
18.6
The Multiple-purpose Retaining Ring ................................................................................ 18-16
18.7
More Work for Round Retaining Rings .............................................................................. 18-18
18.8
Deflections of Perpendicularly Loaded Split Circular Rings .............................................. 18-20
18.9
Improve Design with Retaining Rings ............................................................................... 18-22
Co py rig hte dM ate ria l
Section 19. Balls .....................................................................................................................
19-1
19.1
12 Ways to Put Balls to Work ............................................................................................
19-2
19.2
How Soft Balls Can Simplify Design ..................................................................................
19-4
19.3
Rubber Balls Find Many Jobs ...........................................................................................
19-6
19.4
Multiple Use of Balls in Milk Transfer System ...................................................................
19-8
19.5
Use of Balls in Reloading Press ........................................................................................ 19-10
19.6
Nine Types of Ball Slides for Linear Motion ...................................................................... 19-12
19.7
Stress on a Bearing Ball .................................................................................................... 19-14
19.8
Compact Ball Transfer Units ............................................................................................. 19-16
19.9
Classic Uses of Balls in Valves ......................................................................................... 19-17
Section 20. Bushings & Bearings ..........................................................................................
20-1
20.1
Going Creative with Flanged Bushings .............................................................................
20-2
20.2
Seven Creative Ideas for Flanged Rubber Bushings ........................................................
20-5
20.3
Rotary-linear Bearings .......................................................................................................
20-7
20.4
Unusual Applications of Miniature Bearings ......................................................................
20-8
20.5
Rolling Contact Bearing Mounting Units ............................................................................ 20-10
20.6
Eleven Ways to Oil Lubricate Ball Bearings ...................................................................... 20-12
20.7
Lubrication of Small Bearings ............................................................................................ 20-14
20.8
Cage Keeps Bearings in Line and Lubricated ................................................................... 20-16
Index ..........................................................................................................................................
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I-1
MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
1
Co py rig hte dM ate ria l
INGENIOUS MECHANISMS
Modified Geneva Drives and Special Mechanisms
1-2
Overriding Spring Mechanisms for Low-Torque Drives
1-4
10 Ways to Amplify Mechanical Movement
1-6
10 Ways to Amplify Mechanical Action
1-8
How to Damp Axial and Rotational Motion
1-10
Make Diaphragms Work for You
1-12
4 Ways to Eliminate Backlash
1-14
4 More Ways to Prevent Backlash
1-16
Limit-Switch Backlash
1-18
Copyright © 2005 by The McGraw-Hill Companies
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M o d i f i e d
G e n e v a
D r i v e s
a n d
S p e c i a l
M e c h a n i s m s
These sketches were selected as practical examples of uncommon, but often useful mechanisms. Most of them serve to add a varying velocity component to the conventional Geneva motion.
Co py rig hte dM ate ria l
Sigmund Rappaport Fig. 1—(Below) In the conventional external Geneva drive, a constant-velocity input produces an output consisting of a varying velocity period plus a dwell. In this modified Geneva, the motion period has a constantvelocity interval which can be varied within limits. When spring-loaded driving roller a enters the fixed cam b, the output-shaft velocity is zero. As the roller travels along the cam path, the output velocity rises to some constant valu^, which is less than the maximum output of an unmodified Geneva with the same number of slots; the duration of constant-velocity output is arbitrary within limits. When the roller leaves the cam, the output velocity is zero; then the output shaft dwells until the roller re-enters the cam. The spring produces a variable radial distance of the driving roller from the input shaft which accounts for the described motions. The locus of the roller's path during the constantvelocity output is based on the velocity-ratio desired.
Ou/puf
Input
Ouipuf
fnpuf
Spring
Fig. 2—(Above) This design incorporates a planet gear in the drive mechanism. The motion period of the output shaft is decreased and the maximum angular velocity is increased over that of an unmodified Geneva with the same number of slots. Crank wheel a drives the unit composed of plant gear b and driving roller c. The axis of the driving roller coincides with a point on the pitch circle of the planet gear; since the planet gear rolls around the fixed sun gear d, the axis of roller c describes a cardioid e. To prevent the roller from interfering with the locking disk /, the clearance arc g must be larger than required for unmodified Genevas.
Saxonian Carton Machine Co., Dresden, Germany
Fig. 3—A motion curve similar to that of Fig. 2 can be derived by driving a Geneva wheel by means of a twocrank linkage. Input crank a drives crank b through link c. The variable angular velocity of driving roller d, mounted on b, depends on the center distance L, and on the radii M and N of the crank arms. This velocity is about equivalent to what would be produced if the input shaft were driven by elliptical gears.
Copyright © 2005 by The McGraw-Hill Companies
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Ouiput
Co py rig hte dM ate ria l
Fig. 4—(Left) The duration of the dwell periods is changed by arranging the driving rollers unsymmetrical'ly around the input shaft. This does not affect the duration of the motion periods. If unequal motion periods are desired as well as unequal dwell periods, then the roller crank-arms must be unequal in length and the star must be suitably modified; such a mechanism is called an "irregular Geneva drive."
Output
Fig. 5—(Below) In this intermittent drive, the two rollers drive the output shaft as well as lock it during dwell periods. For each revolution of the input shaft the output shaft has two motion periods. The output displacement
is determined by the number of teeth; the driving angle, ^9 may be chosen within limits. Gear a is driven intermittently by two driving rollers mounted on input wheel b, which is bearing-mounted on frame c. During the dwell period the rollers circle around the top of a tooth. During the motion period, a roller's path d relative to the driven gear is a straight line inclined towards the output shaft. The tooth profile is a curve parallel to path d. The top land of a tooth becomes the arc of a circle of radius R, the arc approximating part of the path of a roller.
Outpuf
fnput
fnpu+
Outpuf
Fig. 6—This uni-directional drive was developed by the author and to his knowledge is novel. The output shaft rotates in the same direction at all times, without regard to the direction of the rotation of the input shaft; angular velocity of the output shaft is directly proportional to the angular velocity of the input shaft. Input shaft a carries spur gear c, which has approximately twice the face width of spur gears / and d mounted on output shaft b. Spur gear c meshes with idler e and with spur gear d. Idler e meshes with spur gears c and /. The output shaft b carries two freewheel disks g and h, which are oriented uni-directionally. When the input shaft rotates clockwise (bold arrow), spur gear d rotates counter-clockwise and idles around free-wheel disk h. At the same time idler e, which is also rotating counter-clockwise, causes spur gear / to turn clockwise and engage the rollers on free-wheel disk g; thus, shaft b is made to rotate clockwise. On the other hand, if the input shaft turns counter-clockwise (dotted arrow), then spur gear / will idle while spur gear d engages free-wheel disk h, again causing shaft b to rotate clockwise.
Copyright © 2005 by The McGraw-Hill Companies
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O v e r r i d i n g f o r
S p r i n g
L o w - T o r q u e
M e c h a n i s m s
D r i v e s
Henry L. MiIo, Jr.
incoming motion to override the outgoing motion whose limit has been reached. In an instrument, for example, the spring device can be placed between
Co py rig hte dM ate ria l
Extensive use is made of overriding spring mechanisms in the design of instruments and controls. Anyone of the arrangements illustrated allows an Stop pin
Take-off fever
Arbor
Drive pin
Fig. 1—Unidirectional Override. The take-off lever of this mechanism can rotate nearly 360 deg. It's movement is limited by only one stop pin. In one direction, motion of the driving shaft also is impeded by the stop pin. But in the reverse direction the driving shaft is capable of rotating approximately 270 deg past the stop pin. In operation, as the driving shaft is turned clockwise, motion is transmitted through the bracket to the take-off lever. The spring serves to hold the bracket against the drive pin. When the take-off lever has traveled the desired limit, it strikes the adjustable stop pin. However, the drive pin can continue its rotation by moving the bracket away from the drive pin and winding up the spring. An overriding mechanism is essential in instruments employing powerful driving elements, such as bimetallic elements, to prevent damage in the overrange regions.
Sprina
Bracket
FIG. 1 Upper pin
drive
Upper bracket
Driving
shaft
Arbor
Stop
A
Stop B
Fig. 2—Two-directional Override. This mechanism is similar to that described under Fig. 1, except that two stop pins limit the travel of the take-off lever. Also, the incoming motion can override the outgoing motion in either direction. With this device, only a small part of the total rotation of the driving shaft need be transmitted to the take-off lever and this small part maybe anywhere in the range. The motion of the driving shaft is transmitted through the lower bracket to the lower drive pin, which is held against the bracket by means of the spring. In turn, the lower drive pin transfers the motion through the upper bracket to the upper drive pin. A second spring holds this pin against the upper drive bracket. Since the upper drive pin is attached to the take-off lever, any rotation of the drive shaft is transmitted to the lever, provided it is not against either stop A or B. When the driving shaft turns in a counterclockwise direction, the take-off lever finally strikes against the adjustable stop A. The upper bracket then moves away from the upper drive pin and the upper spring starts to wind up. When the driving shaft is rotated in a clockwise direction, the take-off lever hits adjustable stop B and the lower bracket moves away from the lower drive pin, winding up the other spring. Although the principal uses for overriding spring arrangements are in the field of instrumentation, it is feasible to apply these devices in the drives of major machines by beefing up the springs and other members.
Take off lever
Upper spring
Spacer
Lower drive pin
Lower
spring
Spacer
Lower bracket
FIG.
Spring
Bracket-
2
Spring
A
Spacers
Arbor lever
Take off lever
Take off lever
Stop B
Spring B
Stop A
FIG. 5
Arbor
pin
Arbor
Fig. 5—Two-directional, 90 Degree Override. This double overriding mechanism allows a maximum overtravel of 90 deg in either direction. As the arbor turns, the motion is carried from the bracket to the arbor lever, then to the take-off lever. Both the bracket and the take-off lever are held against the arbor lever by means of springs A and B. When the arbor is rotated counterclockwise, the takeoff lever hits stop A. The arbor leve'r is held stationary in contact with the takeoff lever. The bracket, which is soldered to the arbor, rotates away from the arbor lever, putting spring A in tension. When the arbor is rotated in a clockwise direction, the take-off lever comes against stop B and the bracket picks up the arbor lever, putting spring B in tension.
Copyright © 2005 by The McGraw-Hill Companies
Arbor Spritig
Arbor lever
Stop
Take off lever FIG. C
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Stop
shaft is free to continue its travel. Six of the mechanisms described here are for rotary motion of varying amounts. The last is for small linear movements.
Co py rig hte dM ate ria l
the sensing and indicating elements to provide overrange protection. The dial pointer is driven positively up to its limit, then stops; while the input
Arbor
Arbor
Spring B
Arbor lever
Drive pin
Take off (ever
Spring A
Bracket Bushing
Spacer washers
Stop A
Spring
Arbor lever
Adjustable stop
Stop B
Brocket
Spring A -
Spring B
Arbor iever
Take off
lever
Stop B
FIG. 3
Take off iever
Stop A
Fig. 3—Two-directional, Limited-Travel Override. This mechanism performs the same function as that shown in Fig. 2, except that the maximum override in either direction is limited to about 40 deg, whereas the unit shown in Fig. 2 is capable of 270 deg movement. This device is suited for uses where most of the incoming motion is to be utilized and only a small amount of travel past the stops in either direction is required. As the arbor is rotated, the motion is transmitted through the arbor lever to the bracket. The arbor lever and the bracket are held in contact by means of spring B, The motion of the bracket is then transmitted to the take-off lever in a similar manner, with spring A holding the take-off lever and the bracket together. Thus the rotation of the arbor is imparted to the take-off lever until the lever engages either stops A or B. When the arbor is rotated in a counterclockwise direction, the take-off lever eventually comes up against the stop B. If the arbor lever continues to drive the bracket, spring A will be put in tension.
FIG. 4
Fig. 4—Unidirectional, 90 Degree Override. This is a single overriding unit, that allows a maximum travel of 90 deg past its stop. The unit as shown is arranged for over-travel in a clockwise direction, but it can also be made for a counterclockwise override. The arbor lever, which is secured to the arbor, transmits the rotation of the arbor to the take-off lever. The spring holds the drive pin against the arbor lever until the takeoff lever hits the adjustable stop. Then, if the arbor lever continues to rotate, the spring will be placed in tension. In the counterclockwise direction, the drive pin is in direct contact with the arbor lever so that no overriding is possible.
Stop B
Stop A
Take off /ever
Fig. 6—Unidirectional, 90 Degree Override. This mechanism operates exactly the same as that shown in Fig. 4. However, it is equipped with a flat spiral spring in place of the helical coil spring used in the previous version. The advantage of the flat spiral spring is that it allows for a greater override and minimizes the space required. The spring holds the take-off lever in contact with the arbor lever. When the take-off lever comes in contact with the stop, the arbor lever can continue to rotate and the arbor winds up the spring.
Input fever
Force
Ptvot
A
Spring
Pivot B
Fig. 7—Two-directional Override, Linear Motion. The previous mechanisms were overrides for rotary motion. The device in Fig. 7 is primarily a double override for small linear travel although it could be used on rotary motion. When a force is applied to the input lever, which pivots about point C, the motion is transmitted directly to the take-off lever through the two pivot posts A and JB. The take-off lever is held against these posts by means of the spring. When the travel is such the take-off lever hits the adjustable stop A1 the take-off lever revolves about pivot post A, pulling away from pivot post B and putting additional tension in the spring. When the force is diminished, the input lever moves in the opposite direction, until the take-off lever contacts the stop B, This causes the take-off lever to rotate about pivot post B, and pivot post A is moved away from the take-off lever.
FIG. 7
Pivot C
Copyright © 2005 by The McGraw-Hill Companies
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1 0
W
a
y
s
t o
M e c h a n i c a l
A m p l i f y M o v e m e n t s
How levers, membranes, cams, and gears are arranged to measure, weigh, gage, adjust, and govern. Federico Strasser
Spring
Co py rig hte dM ate ria l
Stylus
Bridge iever
HIGH AMPLIFICATION for
simple measuring instruments is provided by double lever action. Accuracy can be as high as 0.0001 in.
Measuring points Maximum range
PIVOTED LEVERS allow ex-
tremely sensitive action in comparator-type measuring device shown here. The range, however, is small.
Com to Ilower
Ad justing cam*
Eccentric, com
Spring
Sa ii stylus
ULTRA-HIGH
AMPLIFICA-
TION, with only one lever, is provided in the Hirth-Minimeter shown here. Again, the range is small.
Adjusting corn-
Section through A-A •Worm gear Worm adjustment
Adjustment
Cam tottower FOR CLOSE ADJUSTMENT,
electrical measuring instruments employ eccentric cams. Here movement is reduced, not amplified.
Copyright © 2005 by The McGraw-Hill Companies
Adust men t
•Adjusting spring
MICROSCOPIC ADJUSTMENT ts achieved here by cmploying a large eccentric-cam coupled to a worm-gear drive. Smooth, fine adjustment result.
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Co py rig hte dM ate ria l
CAPSULE UNIT for gaspressure indicators should be provided with a compression spring to preload the membrane for more positive action.
Counterbalancing lever or beam Steelyard rod*
Pointer
Leaf spring
Torque, spring
Load-supporting ie/ers'
Capsufe
LEVER - ACTUATED neighscale needs no springs to maintain balance. The lever system, mounted on knife edges, is extremely sensitive.
Quadrantgear and pinion
AMPLIFIED MEMBRANE MOVEMENT can be gained by the arrangement shown here. A small chain-driven gear links the lever system.
Quadrantgear and Di'nion
Lever
tever
Lea T spring
Torque spring
Stylus QUADRANT-GEAR AND PINION coupled to an Mover provide ample movement of indicator needle foi small changes in governor speed.
Copyright © 2005 by The McGraw-Hill Companies
COMBINATION LEVER AND
GEARED quadrant are used here Io give (he comparator maximum sensitivity combined with ruggedness.
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Drive chain
1 0
W a y s
t o
M e c h a n i c a l
A m p l i f y A c t i o n
Levers, wires, hair, and metal bands are arranged to give high velocity ratios for adjusting and measuring Federico Strasser Adjusfing Adjustment spring
Co py rig hte dM ate ria l
Focusing knob
Rock and pinion
Knife edge
Pivot
L2
Li
Return spring
Stylus
Geared lever
LEVER AND GEAR train amplify the microscope control-knob movement. Knife edges provide friction I ess pivots for lever.
DIAL INDICATOR starts with rack and pinion amplified by gear train. The return-spring takes out backlash.
Spring centertines
Movement
Actuating button
Curved iever
Tension spring
Leaf spring
Stylus rod
VIk cord looped round pulley
Moment orms
Compression Steel spring boil
CURVED LEVER is so shaped and pivoted that the force exerted on the stylus rod, and thus stylus pressure, remains constant.
Stylus or measuring face
Brass wire
Anvil
ZEISS COMPARATOR is provided with a special Ie* ver to move the stylus clear of the work. A steel ball greatly reduces friction.
Copyright © 2005 by The McGraw-Hill Companies
Platinum - iridium hot wire
"HOT-WIRE" AMMETER relies on the thermal expansion of a current-carrying wire. A relatively large needle movement occurs*
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SI eel ribbons
Indicator needle
Opposite-hand twists
Co py rig hte dM ate ria l
Hair Suspension spring
Contact sphere'
STEEL RIBBONS transmit movement without the slightest backlash. The movement is amplified by differences in diameter.
HYGROMETER is actuated by a hair. When humidity causes expansion of the hair, its movement is amplified by a lever.
Square under lest
90° minus the error
Errorte
Swinging rod
ACCURACY of 90° squares can be checked with a device shown here. The rod makes the error much more apparent.
Copyright © 2005 by The McGraw-Hill Companies
METAL BAND is twisted and supported at each end. Small movement of contact sphere produces large needle movement
Support bushing
Short arm attached 1o wire
Steel wire
Micrometer measures movement of b in response to movement of a
TORSIONAL deflection of the short arm is transmitted with low friction to the longer arm for micrometer measurement.
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H o w a n d
t o
D a m p
A x i a l
R o t a t i o n a l
M o t i o n
Fluid-friction devices include two hydraulic and two pneumatic actions; swinging-vane arrangements dissipate energy and govern speed.
Co py rig hte dM ate ria l
Federico Strasser
Control volve
Grid
One-way valve
ADJUSTABLE BYPASS between the two sides of the piston controls speed at which fluid canflowwhen piston is moved.
Locating notch in shaft
CHECK VALVE in piston lets speed be controlled so that the piston moves faster in one direction than in the other.
Spring-grip attachment
ROTATING VANES are resisted by the air as they revolve. Make allowance for sudden stops by providing a spring.
Copyright © 2005 by The McGraw-Hill Companies
SWINGING VANES create increased wind drag as centrifugal force opens them to a larger radius.
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Co py rig hte dM ate ria l Ball valve
Air leaks through adjusting screw
Leather diaphragm
PNEUMATIC CHECK VALVE acts in
FLEXIBLE DIAPHRAGM controls short
manner similar to that of previous device. Vertical position, of course, is necessary.
movements. Speed is fast in one direction, but greatly slowed in return direction.
Stationary position
Copper or aluminum disk
Closed-circuit currents establish their own magnetic field
Springs
Magnet
VANE AREA INCREASES when the
spring-loaded vanes swing out. Forces differ for motion into or against the wind.
Copyright © 2005 by The McGraw-Hill Companies
EDDY CURRENTS are induced in disk when it is moved through a magnetic field. Braking is directly proportional to speed.
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M a k e
D i a p h r a g m s
W o r k
f o r
Y o u
Diaphragms have more uses than you think. Here's a display of applications that simple fabric-elastomer diaphragms can handle economically and with a minimum of design problems.
Co py rig hte dM ate ria l
John R Taplin
Dicphrogm
Diaphragm Atmospheric pressure
Oil connection
inlef
Spring
Pressure passage
Expansion compensator for liquid-filled systems handles thermal expansion of the liquid as well as any system losses*
2
Hydraulic fluid
Force
3
A balanced valve uses a fabric-elastomer diaphragm to hydrostatically balance the valve poppet as well as the valve head.
Inlet
Rolling diaphragm
Hydraulic pressure
Rubber' dust
Piston Spring
seel
Piston
6
Diaphragm
Cylinder
A force-balance load cell converts the weight or force of any object into an accurate reading at a remote point.
Copyright © 2005 by The McGraw-Hill Companies
7
Linear actuator converts gas or fluid pressure into a linear stroke without leakage or break-out friction effects.
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Diaphragms
Co py rig hte dM ate ria l
Piston
D osutb ea l-n c itg eh ae cu tao trdre pn o rv diesbyo fp ralcn h t r u n i t i r i c o i t ig 1w to d ap iha rgm assemeb isl back o tb ack.
Diaphragms
Diaphragms
Oufiet
Outlet
inlet
inlet
Diapnragms
D b e a l-n citgsmp u m pandhascow tiu o d ap io h R e g u n a iltgbyvavleme c o nro tslofh te vd a u lp eha o fb aa rlioug p e r s s u e r a n s a a i r g m o t v i e o o h t n t o u s l 4 anced vavle andw to conro tl d aiph5 a rgm o ts.equ pimentat a sae f wok n rigfw Diaphragms
Diaphragm
Shaft Fluid
8
Shaft seal uses lubricant pressure to force the sidewall of the diaphragm to roll against the shaft and housing.
Orifice
D am n pg im m e cha s n m in p e rven stach an b u r,p s u d d e n o i n t i a m i e 9 amount s i conro teld by oc rfie
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4
W a y s
t o
E l i m i n a t e
B a c k l a s h
Wedges take up freedom in threads and gears, hold shaft snug against bearing. L. Kasper Top cap with upper grooves
Co py rig hte dM ate ria l
Integral rings
THREE INTEGRAL RINGS on shaft slide in grooves to prevent axial movement o( shaft. Grooves in cap are offset axially.
Stud on idle gear
Lower grooves
Driven gear
Clearance hole in idle gear
Stud on driven gear Wedge
Driven gear is keyed to shaft
Pinion SPRING-LOADED WEDGE forces driven and idle gears to move relative in tine another to take up backlash between gears and pinion.
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Clearance
Grooved washer-plates
5-deg taper
Co py rig hte dM ate ria l
Bearing face
Four bolls
Sliding key
Washer plate
CENTRIFUGAL FORCE causes balls to exert force on grooved washer-plates when shaft rotates, pulling it against bearing face.
Collar
Block
COLLAR AND BLOCK have continuous V-thread. When wear takes place in lead screw, the collar always maintains pressure on threads.
Copyright © 2005 by The McGraw-Hill Companies
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4
M o r e
W a y s
t o
P r e v e n t
B a c k l a s h
Springs combine with wedging action to ensure that threads, gears and toggles respond smoothly.
Co py rig hte dM ate ria l
L. Kasper
Idle pinion
Fixedblock
Pinion mounting block
Movable block
Wedge
Movobie block
SPRING-LOADED PINION is mounted on a shaft located so that the spring forces pinion teeth into gear teeth to take up lost motion or backlash.
MOVABLE BLOCK is forced away from fixed block by spring-loaded wedge. Pressure is applied to both sides of lead screw, thus ensuring snug fit.
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Pinion mounting shoft
Co py rig hte dM ate ria l Toggle links
Connecting rod
Stud on connecting rod
Clearance Shaft
Collar on shaft
Collar on worm-
TOGGLE LINKS are spring-loaded and approach alignment to take up lost motion as wear in the joint takes place. Smooth response is thus gained.
HOLLOW WORM has clearance for shaft, which drives worm through pinned collars and links. As wear occurs, springs move worm into teeth.
Copyright © 2005 by The McGraw-Hill Companies
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Link
L i m i t - S w i t c h
B a c k l a s h
Clomp plate
Co py rig hte dM ate ria l
Com adjustment pinion
Corns
Spring
Com followers
Clutch disk Worm geor
Planet gears-
Housing
Com sleeve
Input shaft
Worm gear
SWITCH-ACTUATING CAMS are driven by double-reduction gearing. The first pass is the input worm and its worm gear. The second reduction consists of a planetary system with two keyed planets pivoted on the worm gear. The two planets do not have the same number of teeth. When the worm gear is rotated the planet gears move around a sun gear cast into the base of the housing. The upper planet meshes with gear teeth on the sleeve. The cams clamped to the sleeve actuate the switches. The ratio of the planetary reduction can be altered by changing the planets.
A friction clutch between the sleeve flange and the worm gear makes the switch exceedingly sensitive to reversals at the input worm. When a switch is actuated to reverse input direction, the cams are driven directly by the input worm and gear through the friction clutch until the backlash has been taken up. At this point the clutch begins to slip. The immediate reversal of the cams resets switches in 1A to 1 revolution depending on the worm-gear ratio. In some of the reduction ratios available a deliberate mismatch is employed in planetary gear sizes. This
Copyright © 2005 by The McGraw-Hill Companies
intentional mismatch creates no problems at the pitch velocities produced, since the 3500 rpm maximum at the input shaft is reduced by the stepdown of the worm and worm gear. The low torque requirements of the switch-operating cams eliminate any overstressing due to mismatch. The increased backlash obtained by the mismatch is desirable in the higher reduction ratios to allow the friction clutch to reset the switches before the backlash is taken up. This permits switch reset in less than 1 rpm despite the higher input gear reductions of as much as 1280:1.
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
2
Co py rig hte dM ate ria l
CREATIVE ASSEMBLIES Rotary Ps iton Engn ie Mk li Transfer Syse tm Hydrauc il Moo tr Sa lsh Erors wtih Senstv ie Baalnce Contro-L locked Thwart Vb i rato i n and Shock 1W - ay Oup tut from Speed Reducers Torque-Limtiers Protect Lg iht-Duty Drv ies 6 Ways to Prevent Overo ladn ig 7 More Ways to Prevent Overo ladn ig 7 Ways to Lm i ti Shaft Rotao tin Devc ies for n Idexn ig or Hod ln ig Mechanc ial Movemens t Saw-Mac ti Mechansim Pp in ig Assembyl for Sewage Lift Stato i n Control Vautl Wae tr Bk ie
Copyright © 2005 by The McGraw-Hill Companies
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2-2 2-3 2-4 2-5 2-6 2-8 2-10 2-12 2-14 2-16 2-18 2-19 2-20 2-21
R o t a r y
P i s t o n
E n g i n e
Co py rig hte dM ate ria l
Warren Ogren, Inventor Robert Parmley, Draftsman
Figure 2
End View of Rotary Piston Engine
Figure 1
Exploded drawing of engine illustrates the many standard mechanical components that are arranged to preform a function in a new way.
Figure 3
Cut-Away View of Rotary Piston Engine
Courtesy: Warren Ogren & Morgan & Parmley, Ltd. Copyright © 2005 by The McGraw-Hill Companies
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; V.A.C.
COVER REMOVED
B
ELBOW ADAPTOR)
[WASHES. —• RE LE ASE S
C
Copyright © 2005 by The McGraw-Hill Companies
ON OFF
ATTACH HERE DESIREDWITCHECK VALVE H 600* COUPLING.UNO.11) FOR ALTERNATE ELBOWfiO.S HOOKUP WI8OW)AND TH NO.REPLACE 6(GLASS ASSEMBLEEL-AS TlMfR MOTOR- START AT NO !,SET R0TOR T,M ER SW,TCH ™ ORANGE
(iswimsm
DO NOT OPERATE -EMPTY. NO. 10 WEIGHTUSE OIL.
,SECTIONEt) COVER (25)
VACUUM LINE TUBe
1162 DISCHAR6E VALVE TO TRANSFER STATION OR A SOLUTION TANK
1(ALTERNATE
ALTERNATE DISCHARGE
;«ER
TO FLEXIBLE LINSYSTEM E (5/8FOR ITRANSFER D. TUBING)
Co py rig hte dM ate ria l
POS)-TROL
T r a n s f e r
FACTORY TIMER SETTING ^ SW WHEN 5/8HOSE ID US)NG FLEX. .CYCLE 60 SEC. 45DRAW(OUT) 15 DUMP(IN ) PERMANENT 1ODUMP(IN) WHITE LINtS 30 SEC. 2ODHAW(OUT) SEGMENTS MAYSEADJUSTEDWHtN .WHITE SOLi INSTALLINGEfFICIENCY TO ACHIEVE MAXIMUM SOL BLACK 1 TIMER ALTERNATING ROTOR WIRING DIAGRAM
WALL
w3i$AS>i3JSNvyi woyd
FROMVACUUM SYSTEM
M i l k S y s t e m
Drawn by: Robert O. Parmley
100»! ON 13QOW
Courtesy: Bender Machine Works, Inc.
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Copyright © 2005 by The McGraw-Hill Companies
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VALVE SU8-ASSEMBLY (REMOVE IN ONE UNIT) ONLY REMOVE IN THIS DIRECTION
DKAIN PLUG
RELIEF VALVE
PROTECT THIS SURFACE
Co py rig hte dM ate ria l REMOVE ALL 5 PISTON CONNECTING ROD ASSEMBLIES BEFORE AND CRANKSHAFT
S l a s h
E r r o r s
w i t h
S e n s i t i v e
B a l a n c e
Damping vane.
Co py rig hte dM ate ria l
Balance beam
Compensating elements
Reticle'
Weight fevers
Hanger
Ring weights
Corns
Pan
SENSITIVITY OF BALANCE is independent of temperature fluctuations. To keep the center of gravity constant, two temperature-sensitive elements are riveted to aluminumalloy balance beam, bridging a slot which is directly over the balance point. Their coefficient of expansion compensates for beam deflection caused by variations in temperature.
Enclosed in a cylindrical canister at the rear of the balance beam is a vane that damps its movement, preventing oscillation. The hanger at the front of the scale carries sets of ring weights which are lifted by camoperated levers. The shafts on which the cams are mounted are connected to the mechanical readout. The scale in effect weighs by sub-
Copyright © 2005 by The McGraw-Hill Companies
traction since it is balanced, when empty, by all the ring weights resting on the hanger. To weigh an unknown, the ring weights are lifted from the hanger. The sum of the raised weights is shown on the mechanical counter, which displays the first three digits. The complete total is displayed by the mechanical plus the optical system that projects through the reticle.
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C o n t r o l - L o c k e d a n d
T h w a r t
V i b r a t i o n
S h o c k
Critical adjustments stay put-safe against accidental turning or deliberate fiddling with them.
Co py rig hte dM ate ria l
Frank William Wood, Jr.
•Control knob
Gears
Split yoke
Eccentric
•Sheetmefal finger Stops
Clamp knob
Cam
1..SPLIT YOKE clamps on shaft when eccentric squeezes ends of yoke together. Knurled knob is handy for constant use, and eliminates need for tool. Another advantage is high torque capacity. But this design needs considerable space on panel.
Knurled knob
Split bushing
Lever-
Control shaft
2 . . FINGER springs into place between gear teeth at turn of cam. Although gear lock is ideally suited for right-angle drives, size of teeth limits positioning accuracy.
3 . - SPLIT BUSHING tightens on control shaft, because knurled knob has tapered thread. Bushing also mounts control to panel, so requires just one hole. Lever, like knob, does away with tools, but locks tighter and faster. For controls adjusted infrequently, hex nut turns a fault into an advantage. Although it takes a wrench to turn the nut, added difficulty guards against knobtwisters.
Hex nut-
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Co py rig hte dM ate ria l
Tapered collar
Up
Dial
Tongue
Clomping knob
4 . - CONSTANT DRAG of tapered collar on shaft makes control stiff, so it doesn't need locking and unlocking. Compressed lip both seals out dust and keeps molded locking nut from rotating.
5 . . TONGUE slides in groove, clamps down on edge of dial. If clamp is not tight, it can scratch the face.
Pads
6 . . SPOT-BRAKE clamp is self-locking, which means it takes two hands to make an adjustment, one to hold the clamp open and one to turn the dial.
Thumb-push
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1 - W a y
O u t p u t
f r o m
S p e e d
R e d u c e r s
When input reverses, these five slow-down mechanisms continue supplying a non-reversing rotation.
Co py rig hte dM ate ria l
Louis Slegel
Input
Eccentric cam
Pinion
Traveling gear
Worm
Pawl
input
•Ratchet wheel
Output
Pinion
Output
1 ECCENTRIC CAM adjusts over a range of high-
reduction ratios, but unbalance limits it to low speeds. When direction of input changes, there is no lag in output rotation. Output shaft moves in steps because of ratchet drive through pawl which is attached to TJ-follower.
2 TRAVELING GEAR moves along worm and transfers
drive to other pinion when input rotation changes direction. To ease engagement, gear teeth are tapered at ends. Output rotation is smooth, but there is a lag after direction changes as gear shifts. Gear cannot be wider than axial offset between pinions, or there will be interference.
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Co py rig hte dM ate ria l
Output
Rolling idler
3 ROLLING IDLER also gives smooth output and slight lag after input direction changes. Small drag on idler is necessary, so that it will transfer into engagement with other gear and not sit spinning in between.
Input
Input
Output
Roller clutches
4 TWO BEVEL GEARS drive through roller clutches. One clutch catches in one direction; the other catches in the opposite direction. There is negligible interruption of smooth output rotation when Input direction changes.
Input
Output
5 ROLLER CLUTCHES are on input gears in this
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drive, again giving smooth output speed and little output lag as input direction changes.
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T o r q u e - L i m i t e r s
P r o t e c t
L i g h t - D u t y
D r i v e s
In such drives the light parts break easily when overloaded. These eight devices disconnect them from dangerous torque surges.
Co py rig hte dM ate ria l
L. Kasper
Conical surfaces
Mognef-
Spring
1 MAGNETS transmit torque according to their number and size. In-place control is limited to lowering torque capacity by removing magnets.
2 CONE CLUTCH is formed by mating taper on shaft to beveled hole through gear. Tightening down on nut increases torque capacity.
Ring
Cage
Roller
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3 RING fights natural tendency of rollers to jump out of grooves cut in reduced end of one shaft. Slotted end of hollow shaft is like a cage.
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Roller
Co py rig hte dM ate ria l
Belt
Pins
Arm
4 ARMS hold rollers in slots which are cut across disks mounted on ends of butting shafts. Springs keep rollers in slots; over-torque forces them out.
5 FLEXIBLE BELT wrapped around four pins transmits only lightest loads. Outer pins are smaller than inner pins to ensure contact.
Spring.
Sliding wedges
Drilled passage
6 SPRINGS inside drilled block grip the shaft because they distort during mounting of gear.
Square, rod
7 SLIDING WEDGES clamp down on flattened end of shaft; spread apart when torque gets too high. Strength of springs which hold wedges together sets torque limit.
Disks
8 FRICTION DISKS are compressed by adjustable spring. Square disks lock into square hole in left shaft; round ones lock onto square rod on right shaft.
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6
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These "safety valves" give way if machinery jams, thus preventing serious damage.
Co py rig hte dM ate ria l
Peter C. Noy
Friction faces
Adjusfrble collar
Sprocket
Spring
Shear pin
Collar
Keyway
2
FRICTION CLUTCH. Adjustable spring tension that holds the two friction surfaces together sets overload limit. As soon as overload is removed the clutch reengages. One drawback is that a slipping clutch can destroy itself if unnoticed. Bolt
1
SHEAR PIN is simple to design and reliable in service. However, after an overload, replacing the pin takes a relatively long time; and new pins aren't always available.
3 MECHANICAL KEYS. Spring holds ball in dimple in opposite face until overload forces the ball out. Once slip begins, wear is rapid, so device is poor when overload is common.
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Adjustment screw
Adjustment Slot Rubber pad
Co py rig hte dM ate ria l
Reset hole
Key Ramped keywoy
4 RETRACTING KEY. Ramped sides of key way force key outward against adjustabe spring. As key moves outward, a rubber pad—or another spring—forces the key into a slot in the sheave. This holds the key out of engagement and prevents wear. To reset, push key out of slot by using hole in sheave. Load
Spimed sleeve,
Pinned sleeve
Sliding gear
5
ANGLE-CUT CYLINDER. With just one tooth, this is a simplified version of the jaw clutch. Spring tension sets load limit.
6 Drivingarm
Driver
DISENGAGING GEARS. Axial forces of spring and driving arm balance. Overload overcomes spring force to slide gears out of engagement. Gears can strip once overloading is removed, unless a stop holds gears out of engagement.
Copyright © 2005 by The McGraw-Hill Companies
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7
M o r e
W a y s
t o
P r e v e n t
O v e r l o a d i n g
For the designer who must anticipate the unexpected, here are ways to guard machinery against carelessness or accident.
Co py rig hte dM ate ria l
Peter C. Noy
1
Driving pin
Driven pin
Output shaft
Filled
input shoft
Sleeve
CAMMED SLEEVE connects input and output shafts. Driven pin pushes sleeve to right against spring. When overload occurs, driving pin drops into slot to keep shaft disengaged. Turning shaft backwards resets.
Slot
with powdered iron and oil
Output gear
Magnetic flux,
Overload protection
No overload protection
3
SPRING PLUNGER is for reciprocating motion with possible overload only when rod Is moving left. Spring compresses under overload.
2
MAGNETIC FLUID COUPLING is filled with slurry made of iron or nickel powder in oil. Controlled magnetic flux that passes through fluid varies slurry viscosity, and thus maximum load over a wide range. Slip ring carries field current to vanes.
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Pivots
Fluid-tilted
Co py rig hte dM ate ria l
Vanes
Jaws
Output gear
Soft metal shear pin
S
TENSION RELEASE. When toggle-operated blade shears soft pin, jaws open to release eye. A spring that opposes the spreading jaws can replace the shear pin.
4
FLUID COUPLING. Maximum load can be closely controlled by varying viscosity and level of fluid. Other advantages are smooth transmission and low heat rise during slip.
Piezoelectric crystal
Signal to amplifier and clutch
Steel shot
Output gear,
Yielding ring
Die
7
6 STEEL-SHOT COUPLING transmits more torque as speed increases. Centrifugal force compresses steel shot against case, increasing resistance to slip. Adding more steel shot also increases resistance to slip.
PIEZOELECTRIC CRYSTAL sends output signal that varies with pressure. Clutch at receiving end of signal disengages when pressure on the crystal reaches preset limit. Yielding ring controls compression of crystal.
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7
W a y s
t o
L i m i t
S h a f t
R o t a t i o n
Traveling nuts, clutch plates, gear fingers, and pinning members are the bases of these ingenious mechanisms. I. M. Abeles
Co py rig hte dM ate ria l
IWIechanical stops are often required in automatic machinery and servomechanisms to limit shaft rotation to a given number of turns. Two problems to guard against, however, are: Excessive forces caused by abrupt stops; large torque requirements when rotation is reversed after being stopped.
Troveling nut
Shaft
Traveling nut
Finger,
Stop pin
Shaft
Stop pin
A
Finger
Anchor rod
Frame
TRAVELING NUT moves (1) along threaded shaft until frame prevents further rotation. A simple device, but nut jams so tight that a large torque is required to move the shaft from its
CLUTCH PLATES tighten and stop rotation as the rotating shaft moves the nut against the washer. When rotation is reversed, the clutch plates can turn with the shaft from A to B. During this movement comparatively low torque is required to free the nut from the clutch plates. Thereafter, subsequent movement is free of clutch friction until the action is repeated at other end of the shaft. Device is recommended for large torques because clutch plates absorb energy well.
Rubber
•A
stopped position. This fault is overcome at the expense of increased length by providing a stop pin in the traveling nut (2). Engagement between pin and rotating finger must be shorter
Clutch plates keyed to shaft
than the thread pitch so pin can clear finger on the fir&t reverse-turn. The rubber ring and grommet lessen impact, provide a sliding surface. The grommet can be oil-impregnated metal.
Clutch plates with projection B BeIMtIe washer
Shaft
Rod
Traveling nut
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Section A-A
Metal grommet
B
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B
A Section B-B
idler gear Fixed stop
Rubber shock mount
Co py rig hte dM ate ria l
Finger
Finger,
Gear
Frame
lnitiol
Final
Input shaft
Output
Input gear intermediate
SHAFT FINGER on output shaft hits resilient stop after making less than one revolution. Force on stop depends upon gear ratio. Device is, therefore, limited to low ratios and few turns unless a wormgear setup is used.
input shaft
TWO FINGERS butt together at initial and final positions, prevent rotation beyond these limits. Rubber shock-mount absorbs impact load. Gear ratio of almost 1:1 ensures that fingers will be out of phase with one another until they meet on the final turn. Example: Gears with 30 to 32 teeth limit shaft rotation to 25 turns. Space is saved here but gears are costly.
N fingers rotate on shaft
Finger fixed, to frame
Gear mokes less than one revolution
Pos 2
Pos.l
Pos.l,2,3S4
Shaft
Finger fixed to shaft
Pinion
°os. 3
Input
Frame
shaft
Pas. 5
Pos.4
LARGE GEAR RATIO limits idler gear to less than one turn. Sometimes stop fingers can be added to already existing gears in a train, making this design simplest of all. Input gear, however, is limited to a maximum of about 5 turns.
Copyright © 2005 by The McGraw-Hill Companies
PINNED FINGERS limit shaft turns to approximately N + 1 revolutions in either direction. Resilient pin-bushings would help reduce impact force.
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D e v i c e s
f o r
M e c h a n i c a l
I n d e x i n g
o r
H o l d i n g
M o v e m e n t s
Louis Dodger
Co py rig hte dM ate ria l
Pull knob to release detent
Compression spring
Round-ended detent Detent holes
ROLLER DETENT POSITIONS IN A NOTCH:
RISE,
ROLLER RADIUS,
AXIAL POSITIONING (INDEXING) BY MEANS OF SPACED HOLES IN INDEX BASI
Fiat-sided detent
Retaining pin
Compression spring RADIALLY ARRANGED DETENT HOLDS IN SLOTTED INDEX BASE
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Pi/// knob to release
S
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SIDE
HITCH DETAIL
ELEVATION VIEW
HYDRAULIC NOT SHOWNHOSES
BASIC ASSEMBLY
33(4-REQ1D.)
(4-R EQ'U)
Co py rig hte dM ate ria l
Leo Heikkinen, Inventor Robert Parmley, Draftsman
Courtesy: Dale Heikkinen Copyright © 2005 by The McGraw-Hill Companies
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(ONUV ONE: SHOVJN
B
s
V e
a m
u l
b l y f o r S e
Copyright © 2005 by The McGraw-Hill Companies
w a g e L i f t
Courtesy: Morgan & Parmley, Ltd.
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S t a t i o
PAR.SHALL FLUME
l s
ST(UL//V
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EFFLUENT Dt5CHAGU3E
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AiR. VENT
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-UV UN IT
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SHEAR. GATE REMOVED FOR. BG-Trtf*. Viev^JNG
n i
GRy\XE.
p
C
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VALVt VAULT
C
VALVE
FRO(^ AlR SUPPLY
i
Co py rig hte dM ate ria l
FORCEMAlN
MOUMT FR.OM ceJLJfHG P n
t
W a t e r
B i k e
Co py rig hte dM ate ria l
Drawn by: Robert O. Parmley
Copyright © 2005 by The McGraw-Hill Companies
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
3
Co py rig hte dM ate ria l
LINKAGES 8 Basc i Push-Pul Ln ikages 5 Ln ikages for Strag i ht-Ln i e Moo tin 10 Ways to Change Strag i ht-Ln i e Driecto in 9 More Ways to Change Strag i ht-Ln i e Driecto in Ln ikage for Accee lratn ig and Decee lratn ig Ln iear Strokes Ln ikages for Mutlp iy ln ig Short Moo itns 7 Popua lr Types of Three-Dm i enso inal Drv ies Power Thrust Ln ikages and Theri Appc ilato ins Toggel Ln ikage Appc ilato ins in Dfierent Mechansims 4-Bar Ln ikages and Typc ial Industrial Appc ilato ins
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3-2 3-4 3-6 3-8 3-10 3-12 3-14 3-18 3-20 3-22
8
B a s i c
P u s h - P u l l
L i n k a g e s
These arrangements are invariably the root of all linkage devices. Frank William Wood, Jr. Driving arm
Co py rig hte dM ate ria l
Driving arm
Fixed pivot
Driven arm
Fixed pivots
Driven arm
Linkage arm
Offset arrangement
PUSH-PULL LINKAGE for same direction of motion can be obtained by adding linkage arm to previous design. In both cases, if arms are bars it might be best to make them forked rather than merely flatted at their linkage ends.
FIXED PIVOTS on arm lengths are located to control ratio of input and output movements of this push-pull-actuated linkage. Mechanism can be either flat bars or round rods of adequate thickness to prevent bowing under compression*
Pin attached to driven arm
Driving arm path
Path of driven arm
Guide
Rotary driving arm
Driven arm
Fixed pivot
Driven arm
VERTICAL OUTPUT MOVEMENT from horizontal input is gained with this pushpull linkage. Although the triangularshaped plate could be substituted by an L-shaped arm, the plate gives greater freedom of driving- and driven-arm location.
Copyright © 2005 by The McGraw-Hill Companies
FOR LIMITED STRAIGHT-LINE 2-direction motion use this rotary-actuated linkage. Friction between the pin and sides of slot limit this design to small loads. A bearing on the pin will reduce friction and slot wear to negligible proportions.
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For driving in same direction
Driving
Co py rig hte dM ate ria l
Driven
Driven
Driving
Driven (oppasite direction)
Bearing sieeve
SAME-DIRECTION MOTION is given by this rotary-actuated linkage when end arms are located on the same sides; for opposite-direction motion, locate the arms on opposite sides. Use when a crossover is required between input and output.
ROTARY-ACTUATED LINKAGE gives opposite direction of motion and can be obtained by using 3-bar linkage with pivot point of middle link located at midpoint of arm length. Disk should be adequately strengthened for heavy loads.
Limit stop pin
Fixed pivot
Driving arm.
Rotary driving arm
Equalizing arm
Large radius to provide rotting action against driven arm
Guided arm
Retaining and guide bracket THIS ROTARY-ACTUATED linkage for straight-line 2-direction motion has rotary driving arm with a modified dovetail opening that fits freely around a flat sheet or bar arm. Driven arm reciprocates in slot as rotary driving arm is turned.
Copyright © 2005 by The McGraw-Hill Companies
EQUALIZING LINKAGE here has an equalizing arm that balances the input force to two output arms. This arrangement is most suitable for air or hydraulic systems where equal force is to be exerted on the pistons of separate cylinders.
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5
L i n k a g e s
f o r
S t r a i g h t - L i n e
M o t i o n
These devices convert rotary to straight-line motion without the need for guides.
Co py rig hte dM ate ria l
Sigmund Rappaport
Evans' linkage . . . has oscillating drive-arm that should have a maximum operating angle of about 40°, For a relatively short guide-way, the reciprocating output stroke is large. Output motion is on a true straight line in true harmonic motion. If an exact straight-line motion is not required, however, a link can replace the slide. The longer this link, the closer does the output motion approach that of a true straight line—if link-length equals output stroke, deviation from straight-line motion is only 0.03% of output stroke.
Connecting link
Tracing point
Offset, h
Stroke, S
Arm 1
Arm 2
Copyright © 2005 by The McGraw-Hill Companies
Simplified Watt's linkage . . . generates an approximate straight-line motion. If the two arms are equally long, the tracing point describes a symmetrical figure 8 with an almost straight line throughout the stroke length. The straightest and longest stroke occurs when the connecting-link length is about 2 /3 of the stroke, and arm length is 1.5S. Offset should equal half the connectinglink length. If the arms are unequal, one branch of the figure-8 curve is straighter than the other. It is straightest when a/b equals (arm 2)/(arm 1).
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Co py rig hte dM ate ria l
Driving stroke
Four-bar linkage . . . produces approximately straight-line motion. This arrangement provides motion for the stylus on self-registering measuring instruments. A comparatively small drive-displacement results in a long, almost-straight line.
Output link
Input link (continuous rotation).
D-drive . . . results when linkage arms are arranged as shown here. Output-link point describes a path resembling the letter D, thus it contains a straight portion as part of its cycle. Motion is ideal for quick engagement and disengagement before and after a straight driving-stroke. Example, the intermittentfilm-drivein movie-film projectors.
The "Peaucellier cell" . . . was first solution to the classical problem of generating a straight line with a linkage. Its basis: within the physical limits of the motion, AC x AF remains constant. Curves described by C and F are, therefore, inverse; if C describes a circle that goes through A, then F will describe a circle of infinite radius—a straight line, perpendicular to AB. The only requirements are: AB-BC; AD —AE; and CD, DF, FE, EC are all equal. The linkage can be used to generate circular arcs of large radius by locating A outside the circular path of C.
Copyright © 2005 by The McGraw-Hill Companies
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S t r a i g h t - L i n e
D i r e c t i o n
Arrangements of linkages, slides, friction drives and gears that can be the basis of many ingenious devices.
Co py rig hte dM ate ria l
Federico Strasser
Linkages
Elongated slots
Output
Pivot
Right-angled lever
Input
Basic problem {$ is generally close to 90°)
Slotted lever
Anchored spring
Lever slides
Spherical bearing and housings
Max movement
Rollers
Spring-loaded lever
Spherical bearings
Alternative
arrangements
Pivoted levers with alternative arrangements
Copyright © 2005 by The McGraw-Hill Companies
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Guides Long-trove/ guides Extra guides odd support
Co py rig hte dM ate ria l
Pivots^
Relocated rod
Connecting • rod
Single connecting rod (left) is relocated (right) to get around need for extra guides
Friction
Drives
fnput shaft
Rigid connections
Beit
Drum-
Slide
Beit
Driving member
Inclined bearing-guide
Belt, steel band, or rope around drum, fastened to driving and driven members; sprocket-wheels and chain can replace drum and belt
Gears
Rocks
Rocks
Coupfed pinions
Matching gear-segments
Racks and coupled pinions (can be substituted by friction surfaces for low-cost setup)
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9
M o r e
W a y s
S t r a i g h t - L i n e
t o
C h a n g e
D i r e c t i o n
These devices, using gears, cams, pistons, and solenoids, supplement similar arrangements employing linkages, slides, friction drives, and gears, shown.
Co py rig hte dM ate ria l
Federico Strasser
Rack Gear
Axial screw
identical racks
Articulated rod
Screw
Driven
Identical gears
Driver
InputA
B
Input
Axial screw with rack-actuated gear (A) and articulated driving rod (B) are both irreversible movements, i.e. driver must always drive.
Rack-actuated gear with associated bevel gears is reversible.
Long guide
Articulated rod
Fixed connections
Pivots
Articulated rodInput
Articulated rod on crank-type gear with rack driver. Action is restricted to comparatively short movements.
Cam and spring-loaded follower allow input/output ratio to be varied according to cam rise. Movement is usually irreversible.
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Sliding wedge.
Slide wedge
Co py rig hte dM ate ria l
Offset
Fixed connection
Offset driver
input
Offset driver actuates driven member by wedge action. Lubrication and low coefficient of friction help to allow max offset.
input-
Sliding wedge is similar to previous example but requires spring-loaded follower; also, low friction is less essential with roller follower. Pneumatic, cylinder
Coniroloctuoting stops
Fluid
Two-way valve
Control lever
Input
Compressed air
Fluid coupling is simple, allows motion to be transmitted through any angle. Leak problems and accurate piston-fitting can make method more expensive than it appears to be. Also, although action is reversible it must always be a compressive one for best results.
Pneumatic system with two-way valve is ideal when only two extreme positions are required. Action is irreversible. Speed of driven member can be adjusted by controlling input of air to cylinder.
Auxiliary switches
Two-way switch
Solenoids and two-way switch are here arranged in analogous device to previous example. Contact to energized solenoid is broken at end of stroke. Again, action is irreversible.
Input
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L i n k a g e s
f o r
D e c e l e r a t i n g
A c c e l e r a t i n g L i n e a r
a n d
S t r o k e s
Fig. 1 A slide block with a pinion and shaft and a pin for !ink B reciprocates at a constant rate. The pinion has a crankpin for mounting link D, and it also engages a stationary rack. The pinion can make one complete revolution at each forward stroke of the slide block and another as the slide block returns in the opposite direction. However, if the slide block is not moved through its normal travel range, the pinion turns only a fraction of a revolution. The mechanism can be made variable by making the connection !ink for F adjustable along the length of the element that connects links B and D. Alternatively, the crankpin for link D can be made adjustable along the radius of the pinion, or both the connection link and the crankpin can be made adjustable.
Fig. 2 A drive rod, reciprocating at a constant rate, rocks link BC about a pivot on a stationary block. A toggle between arm B and the stationary block contacts an abutment. Motion of the drive rod through the toggle causes deceleration of driven link B. As the drive rod moves toward theright,the toggle is actuated by encountering the abutment. The slotted link BC slides on its pivot while turning. This lengthens arm B and shortens arm C of link BC. The result is deceleration of the driven link. The toggle is returned by a spring (not shown) on the return stroke, and its effect is to accelerate the driven link on its return stroke.
Co py rig hte dM ate ria l
When ordinary rotary cams cannot be conveniently applied, the mechanisms presented here, or adaptations of them, offer a variety of interesting possibilities for obtaining either acceleration or deceleration, or both.
Drive rod
Rack
Toggle
A
D
B
Pinion
Fig. 2
F
Slide-block
Pivot
B
Abutment*
Stationary block
Fig. 1
C
Th/ck be/t
Driven UnH
Sh'cte-bfocH
Shaft
Fig. 5
Auxiliary block
Spring
Eccentric
Cable
Driven slide block
Driven slide-block
Fig. 6 Fig. 7 Driving slide-block Corbie anchor
Curve at f/ange
Eccentric
Driving $tide*block Source: Mechanisms and Mechanical Devices Sourcebook, 3E, by Chironis & Sclater, © 2001 McGraw-Hill Copyright © 2005 by The McGraw-Hill Companies
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Fig. 5 A constant-speed shaft winds up a thick belt or similar flexible connecting member, and its effective increase in radius causes the slide block to accelerate. It must be returned by a spring or weight on its reversal.
Fig. 4 A bellcrank motion is accelerated as the rollers are spread apart by a curved member on the end of the drive rod, thereby accelerating the motion of the slide block, The driven elements must be returned by spring to close the system.
Fig. 6 An auxiliary block that carries sheaves for a cable which runs between the driving and driven slide block is mounted on two synchronized eccentrics. The motion of the driven block is equal to the length of the cable paid out over the sheaves, resulting from the additive motions of the driving and auxiliary blocks.
Fig. 7 A curved flange on the driving slide block is straddled by rollers that are pivotally mounted in a member connected to the driven slide block. The flange can be curved to give the desired acceleration or deceleration, and the mechanism returns by itself. Fig. 8 The stepped acceleration of the driven block is accomplished as each of the three reciprocating sheaves progressively engages the cable. When the third acceleration step is reached, the driven slide block moves six times faster than the drive rod.
Co py rig hte dM ate ria l
Fig. 3 The same direction of travel for both the drive rod and the drive link is provided by the variation of the Fig. 2 mechanism. Here, acceleration is in the direction of the arrows, and deceleration occurs on the return stroke. The effect of acceleration decreases as the toggle flattens.
Fig. 9 A form-turned nut, slotted to travel on a rider, is propelled by reversing its screw shaft, thus moving the concave roller up and down to accelerate or decelerate the slide block.
Drive roof-
Drive rod-
Tig. 3
Bellcranks
Fig. 4
Toggle
Driven slide^lock
Driven /in K
Abutment
Stationary
bloc/r
Stationary sheave block
Slide-block
Cable
Reciprocating sheaves
Driven slide-b/ocX
Concave roller Drive rod
Form-turned nut
Screw shaft
S/ide blocA:
Fig. 8
Copyright © 2005 by The McGraw-Hill Companies
Rider
Fm. 9
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L i n k a g e s
f o r
M u l t i p l y i n g
S h o r t
M o t i o n s
Co py rig hte dM ate ria l
The accompanying sketches show typical linkages for multiplying short linear motions, usually converting the linear motion into rotation. Although the particular mechanisms shown are designed to multiply the movements of diaphragms or bellows, the same or similar constructions have possible applications wherever it is required to obtain greatly multiplied motions. These transmissions depend on cams, sector gears and pinions, levers and cranks, cord or chain, spiral or screw feed, magnetic attraction, or combinations of these mechanical elements.
Shaft rotated by diaphragm thrust on adjustable ball head screw
Actuating diaphragm
Po'mier Detail
pin
on
Actuating cam /
Double cam
Counterweight
Diaphragm
Lever arm actuates cam on poin ter shaft
Pin on turns
shaft pointer
Pointer
shaft
Re-set cam Fig. 2 A lever and cam drive for a tire gage.
Counterweight
Fig. 1 A lever-type transmission in a pressure gage.
Rocker arm with lever adjustment
Diaphragm stop
Sector gear shaft rotated by lever on rocker shaft
Sector gear turns pointer
Rocker shaft frame adjustment Adjustable lever arm on rocker shafr Fig. 4 A sector gear drive for an aircraft airspeed indicator.
Differential pressure lever
Pointer
Cam
Cord,
Glass
Lever
disk
Spring
Diaphragm moves against lever pin Fig. 3 A lever and sector gear in a differential pressure gage.
FIg. 5 A lever, cam, and cord transmission in a barometer.
Source: Mechanisms and Mechanical Devices Sourcebook, 3E, by Chironis & Sclater, © 2001 McGraw-Hill Copyright © 2005 by The McGraw-Hill Companies
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Diaphragm
Diaphragm
Magnet
Co py rig hte dM ate ria l
Lever arm
Lever arm Fig. 7 A lever system in an automobile gasoline tank.
Thermostatic correef ion
Magne tf mo ved by diaphragm, Controls pointer position magnetically
Fig. 8 Interfering magnetic fields for fluid pressure measurement.
Fig. 6 A link and chain transmission for an aircraft rate of climb instrument.
MuI1/sensitive response
Pointer counterweight
Diaphragm
Sueri'on Pressure Fig. 9 A lever system for measuring atmospheric pressure variations.
Fig. 10 A lever and chain transmission for a draft gage.
Resilient material such as phosphor bronze Diaphragm
Diaphragm
Fig. 11 A toggle and cord drive for a fluid pressure measuring instrument.
Fig. 12 A spiral feed transmission for a genera! purpose analog instrument.
Copyright © 2005 by The McGraw-Hill Companies
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S e v e n o f
P o p u l a r
T y p e s
T h r e e - D i m e n s i o n a l
D r i v e s
Main advantage of three-dimensional drives is their ability to transit motion between nonparallel shafts. They can also generate other types of helpful motion. With this roundup are descriptions of industrial applications.
Co py rig hte dM ate ria l
Dr. W. Meyer Zur Capellen
1
The Spherical Crank
2
spherical crank
drive
This type of drive is the basis for most 3-D linkages, much as the common 4-bar linkage is the basis for the two-dimensional field. Both mechanisms operate on similar principles. (In the accompanying sketches, a is the input angle, and /3 the output angle. This notation has been used throughout the article.) In the 4-bar linkage, the rotary motion of driving crank I is transformed into an oscillating motion of output link 3. If the fixed link is made the shortest of all, then you have a double-crank mechanism, in which both the driving and driven members make full rotations. In the spherical crank drive, link 1 is the input, link 3 the output. The axes of rotation intersect at point O; the lines connecting AB, BC7 CD and DA can be thought of as part of great circles of a sphere. The length of the link is best represented by angles a, b, c and d.
spherical-slide oscillator The two-dimensional slider crank is obtained from a 4-bar linkage by making the oscillating arm infinitely long. By making an analogous change in the spherical crank, you can obtain the spherical slider crank shown at right. The uniform rotation of input shaft I is transferred into a nonuniform oscillating or rotating motion of output shaft III. These shafts intersect at an angle 8 corresponding to the frame link 4 of the spherical crank. Angle 7 corresponds to length of link L Axis II is at right angle to axis III. The output oscillates when y is smaller than 8; the output rotates when y is larger than 8. Relation between input angle a and output angle JB is (as designated in skewed Hook's joint, below)
Spherical-Slide .-Oscillator
Copyright © 2005 by The McGraw-Hill Companies
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Worm dhveshaft-
Worm wheel
Top view
Co py rig hte dM ate ria l
Skewed Hook's MM
Side view
Woshing-Machine Mechanism
3
skewed hook's joint
Dough- Kneading Mechanism
This variation of the spherical crank is often used where an almost linear relation is desired between input and output angles for a large part of the motion cycle. The equation defining the output in terms of the input can be obtained from the above equation by making S — 90°. Thus sin 8 = 1, cos S = 0, and
Output rotation, /S, deg
The principle of the skewed Hook's joint has been
recently applied to the drive of a washing machine (see sketch at left). Here, the driveshaft drives the worm wheel 1 which has a crank fashioned at an angle y. The crank rides between two plates and causes the output shaft III to oscillate in accordance with the equation above. The dough-kneading mechanism at right is also based on the Hook's joint, but utilizes the path of link 2 to give a wobbling motion that kneads dough in the tank.
Double Universal Joint
4
the universal joint The universal joint is a variation of the spherical-slide oscillator, but with angle y ~ 90°. This drive provides a totally rotating output and can be operated as a pair, as shown above. Equation relating input with output for a single uni-
Copyright © 2005 by The McGraw-Hill Companies
Pulsating motion
Uniform motion
Input rotation a, deg Input-output relationship
versal joint, where B is angle between connecting link and shaft I: Output motion is pulsating (see curve) unless the joints are operated as pairs to provide a uniform motion.
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5
Co py rig hte dM ate ria l
Plane Crank Slide
the 3-D crank slide
The three-dimensional crank slide is a variation of a plane crank slide (see sketch), with a ball point through which link g always slides, while a point B on link g describes a circle. A 3-D crank is obtained from this mechanism by making output shaft III not normal to the plane of the circle; another way is to make shafts I and III nonparallel. A practical variation of the 3-D crank slide is the agitator mechanism (right). As input gear I rotates, link g swivels around (and also lifts) shaft III. Hence, vertical link has both an oscillating rotary motion and a sinusoidal
6
Input shaft
Agitator Mechanism
harmonic translation in the direction of its axis of rotation. The link performs what is essentially a screw motion in each cycle.
the elliptical slide The output motion, ft, of a spherical slide oscillator, p 23-12, can be duplicated by means of a two-dimensional "elliptical slide." The mechanism has a link g which slides through a pivot point D and is fastened to a point P moving along an elliptical path. The ellipse can be generated by a Cardan drive, which is a planetary gear system with the planet gear half the diameter of the internal gear. The center of the planet, point M, describes a circle; any point on its periphery describes a straight line, and any point in between, such as point P, describes an ellipse. There are certain relationships between the dimensions of the 3-D spherical slide and the 2-D elliptical slide: tan y/sin 8 = z/d and tan y/cot S — b/d, where a is the major half-axis, b the minor half-axis of the ellipse, and d is the length of the fixed link DN. The minor axis lies along this link. If point D is moved within the ellipse, a completely rotating output is obtained, corresponding to the rotating spherical crank slide.
Copyright © 2005 by The McGraw-Hill Companies
The Elliptical Slide
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Crank Input shaft (rotates)
Connecting rod
Rocker Stationary frame
Co py rig hte dM ate ria l
Output shaft (oscillates) Stationary frame
(A) Basic Configuration
(B) Its Inversion
(C) Asa 90° Uniform Motion Transmitter
7
the space crank
One of the most recent developments in 3-D linkages is the space crank shown in (A) see also PE-"Introducing the Space Crank—a New 3-D Mechanism/' Mar 2 '59. It resembles the spherical crank discussed on page 76, but has different output characteristics. Relationship between input and output displacements is:
Velocity ratio is:
Copyright © 2005 by The McGraw-Hill Companies
where ojft is the output velocity and w, is the constant input velocity. An inversion of the space crank is shown in (B). It can couple intersecting shafts, and permits either shaft to be driven with full rotations. Motion is transmitted up to 37£° misalignment. By combining two inversions, (C), a method for transmitting an exact motion pattern around a 90° bend is obtained. This unit can also act as a coupler or, if the center link is replaced by a gear, it can drive two output shafts; in addition, it can be used to transmit uniform motion around two bends.
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P o w e r T h e i r
T h r u s t
L i n k a g e s
a n d
A p p l i c a t i o n s
POWERED STRAIGHT LINE MOTION over
Fig. 4—Constant thrust toggle. Pressure is same at all points of throw. Fig. 5—Multiplying motion, 6 to 1, might be used for screen shift. Fig. 6—Bell crank and toggle may be applied in embossing press, extruder or die-caster. Fig. 7—Horizontal pull used for clay pigeon traps, hopper trips, and sliding elements with spring or counterweighted return. Fig. 8—Shipper rod for multiple and distant operation as series of valves. Fig. 9—Door opener. Upthrust of helical racks rotates gear and arm. Fig. 10—Accelerated motion by shape of cam such as on a forging hammer. Fig. 11—Intermittent lift as applied to lifting pipe from well. Fig. 12—Straight-line motion multiplied by pinion and racks.
Fig. 13—Rotary motion with cylindrical cam. Operates gate on conveyor belt. Fig. 14—Thrust motions and "dwells" regulated by cam. Fig. 15—Four positive positions with two Thrustors. Fig. 16—Toggle increasing thrust at right angle. Fig. 17—Horizontal straight-line motion as applied to a door opener. Fig. 18—Thrusts in three directions with two Thrustors. Fig. 19—Fast rotary motion using step screw and nut. Fig. 20—Intermittent rotary motion. Operated by successive pushing of operating button, either manually or automatically. Fig. 21—Powerful rotary motion with worm driven by rack and pinion.
Co py rig hte dM ate ria l
short distances is applicable to many types of machines or devices for performing specialized services. These motions can be produced by a steam, pneumatic or hydraulic cylinder, or by a self-contained electric powered unit such as the General Electric Thrustors shown herewith. These Thrustors may be actuated manually by pushbuttons, or automatically by mechanical devices or the photo-electric relay as with a door opener. These illustrations will suggest many other arrangements.
Fig. 1—Transfer motion to distant point. Fig. 2—Double throw by momentary applications. Fig. 3~Trammel plate divides effort and changes directions of motion.
FIG.2
FI6.1
FIG.6
FIG.4
FIG.3
FIG.5
FIG.7
FIG. 8
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l FIG. 11
FlG.9
FIG.IO
FIG.12
FlG. 14
FlG.13
FlG. 15
FIG.17
FIG.16
FlG. 18
FIG.19
Copyright © 2005 by The McGraw-Hill Companies
FIG.20
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FlG. 21
T o g g l e i n
L i n k a g e
D i f f e r e n t
A p p l i c a t i o n s
M e c h a n i s m s
Thomas P. Goodman
Fa
Applied force
Co py rig hte dM ate ria l
Fc
C
Resisting force
0 Applied force (A)
Fig. I
Mechanical advantage
(B)
Fig 2
FORCES CAN BE APPLIED through other links, and need not be perpendicular to each other. (A) One toggle link can be attached to another link rather than to a fixed point or slider. (B) Two toggle links can come into toggle by lining up on top of each other rather than as an extension of each other. Resisting force can be a spring force.
MANY MECHANICAL LINKAGES are based on the simple toggle which consists of two links that tend to line-up in a straight line at one point in their motion. The mechanical advantage is the velocity ratio of the input point A to the output point B; or VAIVB, AS the angle a approaches 90 deg, the links come into toggle and the mechanical advantage and velocity ratio both approach infinity. However, frictional effects reduce the forces to much less than infinity although still quite high.
HIGH MECHANICAL
ADVANTAGE Load
IN PUNCH PRESSES, large forces are needed at the lower end of the work-stroke, however little force is required during the remainder. Crank and connecting rod come into toggle at the lower end of the punch stroke, giving a high mechanical advantage at exactly the time it is most needed.
fig. 3
Force
Latching force
Stop
(A)
Toggle position
Fig. 5
(B)
Unlatching force
COLD-HEADING RIVET MACHINE is designed to give each rivet two successive blows. Following the first blow (point 2) the hammer moves upward a short distance (to point 3), to provide clearance for moving the workpiece. Following the second blow (at point 4), the hammer then moves upward a longer distance (to point 1). Both strokes are produced by one revolution of the crank and at the lowest point of each stroke (points 2 and 4) the links are in toggle.
Unlatching force
LOCKING LATCHES produce a high mechanical advantage when in the toggle portion of the stroke. (A) Simple latch exerts a large force in the locked position. (B) For positive locking, closed position of latch is slightly beyond toggle position. Small unlatching force opens linkage.
Fnctton shoes
Crank
Fig 6
n
Arm I
Fig 4
Fig 7
Short stroke I ong stroke
STONE CRUSHER uses two toggle linkages in series to obtain a high mechanical advantage. When the vertical link I reaches the top of its stroke, it comes into toggle with the driving crank II; at the same time, link III comes into toggle with link IV. This multiplication results in a very large crushing force.
Copyright © 2005 by The McGraw-Hill Companies
FRICTION RATCHET is mounted on a wheel; light spring keeps friction shoes in contact with the flange. This device permits clockwise motion of the arm I. However, reverse rotation causes friction to force link II into toggle with the shoes which greatly increases the locking pressure.
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HIGH VELOCITY RATIO DOOR CHECK LINKAGE gives a high velocity ratio at one point in the stroke. As the door swings closed, connecting link I comes into toggle with the shock absorber arm II, giving it a large angular velocity. Thus, the shock absorber is more effective retarding motion near the closed position.
Co py rig hte dM ate ria l
Open position W
Large ratio invelocity this region
Closed position Fig. 8
Fig 9
Shock absorber
VARIABLE MECHANICAL Open position
Closed contacts
IMPACT REDUCER used on some large circuit breakers. Crank I rotates at constant velocity while lower crank moves slowly at the beginning and end of the stroke. It moves rapidly at the mid stroke when arm II and link III are in toggle. Falling weight absorbs energy and returns it to the system when it slows down.
ADVANTAGE
Fig 12
Operating lever
Center distance
(A)
Ftg IO
(C)
TOASTER SWITCH uses an increasing mechanical advantage to aid in compressing a spring. In the closed position, spring holds contacts closed and the operating lever in the down position. As the lever is moved upward, the spring is compressed and comes into toggle with both the contact arm and the lever. Little effort is required to move the links through the toggle position; beyond this point, the spring snaps the contacts closed.
A
Differential screw
(D)
FOUR-BAR LINKAGES can be altered to give variable velocity ratio (or mechanical advantage). (A) Since the cranks I and II both come into toggle with the connecting link III at the same time, there is no mechanical advantage. (B) Increasing the length of link III gives an increased mechanical advantage between positions 1 and 2, since crank I and connecting link III are near toggle. (C) Placing one pivot at the left produces similar effects as in (B). (D) Increasing the center distance puts crank II and link NI near toggle at position 1; crank I and link III approach toggle position at 4.
B
(B)
Upper plate
Hand wheel Fig M
Lower plate
Piston Riveter head attached to slide
TOGGLE PRESS has an increasing mechanical advantage to counteract the resistance of the material being compressed. Rotating handwheel with differential screw moves nuts A and B together and links I and II are brought into toggle.
Copyright © 2005 by The McGraw-Hill Companies
Fig.13
RIVETING MACHINE having a reciprocating piston produces high mechanical advantage with the linkage shown. With a constant piston driving force, the force of the head increases to a maximum value when links II and III come into toggle.
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F
o
u
r
-
B
a
r
L
i
n
k
a
g
e
s
a
n
d
T y p i c a l
I n d u s t r i a l
A p p l i c a t i o n s
AU mechanisms can be broken down into equivalent four-bar linkages. They can be thought of as the basic mechanisms and are useful in many mechanical operations. c
Co py rig hte dM ate ria l
C C
B
A
6
A
D
B
A
D
D
FOUR-BAR LINKAGE~Two cranks, a connecting rod and a line between the fixed centers of the cranks make up the basic four-bar linkage. Cranks can rotated if A is smaller than B or C or D, Link motion can be predicted.
CRANK AND ROCKER — Following relations must hold for operation:
C
A
FOUR-BAR LINK WITH SLIDING MEMBER—One crank replaced by circular slot with effective crank distance of B.
A+B+OD; A+D+B>C; ,4+CBD.
B.
C
r
B
D
A.
V
B
D
C
PARALLEL CRANK FOUR-BAR—Both cranks of the parallel crank four-bar linkage always turn at the same angular speed but they have two positions where the crank cannot be effective. They are used on locomotive drivers.
Al
DOUBLE PARALLEL CRANK—This mecanism avoids dead center position by having two sets of cranks at 90 deg -advancement. Connecting rods are always parallel. Sometimes used on driving wheels ©i locomotives.
A
PARALLEL CRANKS—Steam control linkage assures equal valve openings.
C
C
A
D
D
D
B1
B
A
B,
C
NON-PARALLEL EQUAL CRANK— The centrodes are formed as gears for passing dead center and can replace ellipticals.
SLOW MOTION LINK—As crank A is rotated upward it imparts motion to crank B. When A reaches dead center position, the angular velocity of crank B decreases to zero. This mechanism is used on the Corliss valve.
TRAPAZOIDAL LINKAGE—This linkage is not used for complete rotation but can be used for special control. Inside moves through larger angle than outside with normals intersecting on extension of rear axle in cars.
T SIM*
DOUBLE PARALLEL CRANK MECHANISM—This mechanism forms the basis for the universal drafting machine.
ISOSCELES DRAG LINKS—"LazyTong" device made of several isosceles links; used for movable lamp support.
Copyright © 2005 by The McGraw-Hill Companies
WATT'S STRAIGHT-LINE MECHANISM—Point T describes line perpendicular to parallel position of cranks.
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Co py rig hte dM ate ria l
Line of centers
Crank
STRAIGHT SLIDING LINK—This is the form in which a slide is usually used to replace a link. The line of centers and the crank B are both of infinite length.
DRAG LINK—This linkage used as the drive for slotter machines. For complete rotation: B>A+D~C and B
NON-PARALLEL EQUAL CRANK—If crank A has uniform angular speed, B will vary.
ELLIPTICAL GEARS—They produce same motion as non-parallel equal cranks.
TREADLE DRIVE—This four-bar linkage is used in driving grindwheels and sewing machines.
+C-A.
DOUBLE LEVER MECHANISM—Slewing crane can move load in horizontal direction by using D-shaped portion of top curve.
ROBERTS STRAIGHT-LINE MECHANISM—The lengths of cranks A and B should not be less than 0.6 D ; C is one half D.
TCHEBICHEFF'S— Links made in pro-
portion: AB=CD^20, AD=16, BO=8.
Copyright © 2005 by The McGraw-Hill Companies
ROTATING CRANK MECHANISM— This linkage is frequently used to change a rotary motion to swinging movement.
NON-PARALLEL EQUAL CRANK— Same as first but with crossover points on link ends.
PANTOGRAPH—The pantograph is a parallelogram in which lines through F, G and H must always intersect at a common point.
PEUCELLIER'S CELL — When proportioned as shown, the tracing point T forms a straight line perpendicular to the axis.
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
4
Co py rig hte dM ate ria l
CONNECTIONS 14 Ways to Fasten Hubs to Shafts Atachn ig Hubelss Gears to Shafts 10 Dfierent Types of Spn iled Conneco itns Atlernates for Doweeld Fasteners 6 More Atlernates for Doweeld Fastenn igs 29 Ways to Fasten Sprn igs 20 TamperP -roof Fasteners Lanced Metal Em il n iates Separate Fasteners Jon in ig Cricua lr Parts wth iout Fasteners
Copyright © 2005 by The McGraw-Hill Companies
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4-2 4-4 4-6 4-8 4-10 4-12 4-16 4-18 4-20
1 4
W a y s
to
F a s t e n
H u b s
to
S h a f t s
M. Levine
Shoulder may be needed on shaft
Pin through shaft
Set screw Square key Hub
Co py rig hte dM ate ria l
Flat on shaft
Shaft
(A)
Set screw (B)
(C)
1 Cup-point setscrew . . . in hub (A) bears against flat on shaft. Fastening suitable for fractional horsepower drives with low shock loads. Unsuitable when frequent removal and assembly necessary. Key with setscrew (6) prevents shaft marring from frequent removal and assembly. Not suitable where high concentricity is required.
(D)
Taper pin (E)
Can withstand high shock loads. Two keys 120° apart (C) transmit extra heavy loads. Straight or tapered pin (D) prevents end play. For experimental setups expanding pin is positive yet easy to remove. Gear-pinning machines are available. Taper pin (E) parallel to shaft may require shoulder on shaft. Can be used when gear or pulley has no hub.
Straight-sided 4-spline (involute splines may also be used)
4 Splined shafts . . . are frequently used when gear must slide. Square splines can be ground to close minor diameter fits but involute splines are self-centering and stronger. Non-sliding gears may be pinned to shaft if provided with hub.
Spacer ring
End plates
Tapered rings
Interlocking... tapered rings hold hub tightly to shaft when nut is tightened. Coarse tolerance machining of hub and shaft does not effect concentricity as in pinned and keyed assemblies. Shoulder is required (A) for end-of-shaft mounting; end plates and four bolts (B) allow hub to be mounted anywhere on shaft.
(A)
Copyright © 2005 by The McGraw-Hill Companies
(B)
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Tapered rings
Key Keyway
Taper
(B)
(A)
Tapered s h a f t . . . with key and threaded end provides rigid, concentric assembly. Suitable for heavy-duty applications, yet can be easily dissasembled. 2
Feather key
Feather key
Co py rig hte dM ate ria l
Keyway
3 Feather key . . . (A) allows axial movement. Keyway must be milled to end of shaft. For blind keyway (B) hub and key must be drilled and tapped, but design allows gear to be mounted anywhere on shaft with only a short keyway. Lugs stamped after assembly
Gear or pbl/ey
Shoulder
Pin
One-piece wire
Retaining ring
Retaining ring . . . allows quick removal in light load applications. Shoulder on shaft necessary. Pin securing gear to shaft can be shear-pin if protection against excessive load required. 5
6 Stamped g e a r . . . and formed wire shaft used mostly in toys. Lugs stamped on both legs of wire to prevent disassembly. Bend radii of shaft shoukl be small enough to allow gear to seat.
For tightening on shaft: Hub half of hole threaded. Bushing half of hole not threaded.
Hub clomp
Slotted hub
For removing from shaft; Bushing naif of hoie threaded. Hub half of hole not threaded.
8 Split bushing . . . has tapered outer diameter. Split holes in bushing align with split holes in hub. For tightening, hub half of hole is tapped, bushing half is un-tapped. Screw therefore pulls bushing into hub as screw is screwed into hub. Bushing is jacked from hub by a reverse procedure. Sizes of bushings available for V2- to 10-in. dia shafts. Adapters are available for untapered hubs.
Slight clearance
9 Split h u b . . . of stock precision gear is clamped onto shaft with separate hub clamp. Manufacturers list correctly dimensioned hubs and clamps so that efficient fastening can be made based on precision ground shaft. Idea! for experimental set-ups.
Copyright © 2005 by The McGraw-Hill Companies
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A t t a c h i n g
H u b l e s s
G e a r s
t o
S h a f t s
Thin gears and cams save space—but how to fasten them to their shafts? These illustrated methods give simple, effective answers.
Pins
Co py rig hte dM ate ria l
L. Kasper
1 COUNTERBORE with close fit on shaft ensures concentric mounting. Torque is transmitted by pins; positive fastening is provided by flathead screw.
Counterbore
Shaft
Plate
Washer,
2 TIGHT-FITTING washer in counterbored hole carries the radial load; its shear area is large enough to ensure ample strength.
3 PLATE gives greater resistance to shear when radial loads are likely to be heavy. When the gear is mounted, the plate becomes the driver; the center screw merely acts as a retainer.
Copyright © 2005 by The McGraw-Hill Companies
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Key
D-plate
Taper pin:
Co py rig hte dM ate ria l
Oversize slot
Pm length-
Fiat ground on taper pin
Gear width
4 KEY AND FLATTED TAPER-PIN should not protrude above surface of gear; pin length should be slightly shorter than gear width. Note that this attachment is not positive—gear retention is by friction only.
5 D-PLATE keys gear to shaft; optimum slot depth in shaft will depend upon torque forces and stop-and-start requirements—low, constant torque requires only minimum depth and groove length; heavy-duty operation requires enough depth to provide longer bearing surface.
Spanner holes
Split taper-plug
Taper
Flush or slightly sunk plug surfaces
6 TAPERED PLUG is another friction holding device. This type mounting should be used so that the radial load will tend to tighten rather than loosen the thread. For added security, thread can be lefthand to reduce tampering risk.
Disks
7 TWO FRICTION DISKS, tapered to about 5° included angle on their rims, are bored to fit the shaft. Plathead screws provide clamping force, which can be quickly eased to allow axial or radial adjustment of gear.
Slot
Slot
Pins
8 TWO PINS in radial hole of shaft provide positive drive that can be easily disassembled. Pins with conical end are forced tightly together by flathead screws. Slot length should be sufficient to allow pins to be withdrawn while gear is in place if backside of gear is "tight" against housing.
Copyright © 2005 by The McGraw-Hill Companies
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1
0
D i f f e r e n t
T
y
p
e
s
o f
S
p
l
i
n
e
d
C
o
n
n
e
c
t
i
o
n
W. W. Heath
Taper 0.75"per foot
TYPES
Co py rig hte dM ate ria l
CYLI NDRICAL
Tooth Proportions Addendum (ext.) Addendum (int.) Total depth
I
SQUARE SPLINES make a simple connection and are used mainly for applications of light loads, where accurate positioning is not important. This type is commonly used on machine tools; a cap screw is necessary to hold the enveloping member.
SERRATIONS of small size are used mostly for applications of light loads. Forcing this shaft into a hole of softer material makes an inexpensive connection. Originally straight-sided and limited to small pitches, 45 deg serrations have been standardized (SAE) with large pitches up to 10 in. dia. For tight fits, serrations are tapered.
2
(B) Tooth width fit
Major diameter fit (A)
Addendum
Minor diameter fit
5
INVOLUTE-FORM splines are used where high loads are to be transmitted. Tooth proportions are based on a 30 deg stub tooth form. (A) Splined members may be positioned either by close fitting major or minor diameters. (B) Use of the tooth
FACE
Oiom pitch
width or side positioning has the advantage of a full fillet radius at the roots. Splines may be parallel or helical. Contact stresses of 4,000 psi are used for accurate, hardened splines. Diametral pitch above is the ratio of teeth to the pitch diameter.
Addendum
TYPES
Oedendum
Sectional view (A)
(B) Pitch FELLOWS GEAR SHAPER CC
8
MILLED SLOTS in hubs or shafts make an inexpensive connection. This type is limited to moderate loads and requires a locking device to maintain positive engagement. Pin and sleeve method is used for Hght torques and where accurate positioning is not required.
Copyright © 2005 by The McGraw-Hill Companies
Q RADIAL SERRATIONS by milling or shaping the ' teeth make a simple connection. (A) Tooth proportions decrease radially. (B) Teeth may be straight-sided (castellated) or inclined; a 90 deg angle is common.
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s
Tooth Proportions
Co py rig hte dM ate ria l
SAE STANDARD SPLINE PROPORTIONS
No. of splines 4 Spline width W
6 IOorl6
External
Tight fit h Uno l aded h Sliding fit loaded h
Internal member
Width of 16-tooth spline is 0.098D Root dia,d = D-2h
Ground lands
STRAIGHT-SIDED splines have been widely used in the automotive field. Such splines are often used for sliding members. The sharp corner at the root limits the torque capacity to pressures of approximately 1,000 psi on the spline projected area. For different applications, tooth height is altered as shown in the table above.
3
GOULD ANO EBERHART CO.
1 MACHINE-TOOL spline has a wide gap between " splines to permit accurate cylindrical grinding of the lands—for precise positioning. Internal parts can be ground readily so that they will fit closely with the lands of the external member.
Enlarged sectfon
8AR8ER-C0LMAN CO.
Snap ring holds assembly together
SPECIAL INVOLUTE splines are made by using gear tooth proportions. With full depth teeth, greater contact area is possible. A compound pinion is shown made by cropping the smaller pinion teeth and internally spHning the larger pinion.
6
TAPER-ROOT splines are for drives which require positive positioning. This method holds mating parts securely. With a 30 deg involute stub tooth, this type is stronger than parallel root splines and can be hobbed with a range of tapers.
7
Outside cutting surface
Straight-sided tooth form
Concave teeth
Annular\ cutter
Inside cutting surface
Convex teeth
(A) 30 degree tooth form
•j A CURVIC COUPLING teeth are machined by a face-mill IW type of cutter. When hardened parts are used which require accurate positioning, the teeth can be ground. (A) This process produces teeth with uniform depth and can be cut at
GLEASON GEAR WORKS (B)
any pressure angle, although 30 deg is most common. (B) Due to the cutting action, the shape of the teeth will be concave (hour-glass) on one member and convex on the other—the member with which it will be assembled.
Copyright © 2005 by The McGraw-Hill Companies
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A l t e r n a t e s
f o r
D o w e l e d
F a s t e n e r s
Some simple ways to fasten or locate round or flat parts without having to use dowels or other pins.
Co py rig hte dM ate ria l
Federico Strasser
Alternate grooving s
'Countersink offer assembly
Shoulders
SETSCREW through hub of wheel or other circular part is superior to a dowel when angular adjustment must be made— note alternate groovings.
SHOULDER on shaft lets gear or disk be held at end of shaft. Two alternative ways are shown—a dowel would not be too practical here.
After staking
After staking
STAKING either the shaft or the attached part is ideal for light loads, Various stake patterns are shown— staking can be done either by hand or by machine (I\K—Sep 4 '61, page 354). Two advantages of this method of fastening parts onto shafts are low cost and assembly speed.
Copyright © 2005 by The McGraw-Hill Companies
staking patterns
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Co py rig hte dM ate ria l
Wheel hub
Large clearance hole
Handle or arm
Axial location depends on loper and o'lomaters
PRESSURE JOINTS are best when large composite wheels or similar parts are to be fastened to their shafts with only one or two screws.
TAPERED JOINTS are ideal when no clearance can be allowed between hub and shaft. Dowelling would be impracticable because of fit.
Braze or solder
Adhesive or varnish
B
A
C PERMANENT FASTENINGS of parts assembled to shafts are crimped (A); soldered, bra/ed or welded (B) or adhesive-held (C). Non-permanent fastening of small indicator-pointer is best achieved by providing simple push fit (I)). If positive location is required here, dimple hub after assembly.
Copyright © 2005 by The McGraw-Hill Companies
D
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6 More Alternates for Doweled Fastenings These simple but effective methods fasten or locate round and flat plates without dowels or other pins.
Co py rig hte dM ate ria l
Federico Strasser
TORQUE LIMtTERS are necessary in many cases where a doweled fastening would be useless. If shaft load becomes excessive a low-cost means of providing for its disengagement is to have a springloaded ball mounted externally (A) or internally (B).
Adjusting screw
External ball
SHEET METAL "DOWELS" can be used where locution of two parts is needed without precise hole location. Cup is drawn after assembly.
Copyright © 2005 by The McGraw-Hill Companies
Infernal boll (no means of adjustment}
SELF-DOWELING pan can be sheef metal (A) or other thin-material part (B). Merely emboss or punch slug halfway through to locate in hole.
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Co py rig hte dM ate ria l
BASIC FRICTION-CLUTCH can also provide for disengagement when torque exceeds a safe value* There is basically no difference between collared shaft (A) and ringed shaft (B), but adjustment of tension in collared shaft is limited by amount of threading on end of shaft.
Adjustment range
Maximum adjustment
A
B
A
B
C
Flattened wings
D
FOLDED ASSEMBLIES eliminate the need for pins or other locating fasteners. Illustrated is a terminal mounted on insulating plates.
SPLINES such as square (A) and involute (B) are often the best way to locate and hold hubs. Don't overlook simpler methods shown'AtC and I).
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
2 9
W a y s
t o
F a s t e n
S p r i n g s
Four pages of ingenious attachments for extension, compression, and torsion springs. Federico Strasser
E X T E N S I O N SPRINGS
Co py rig hte dM ate ria l
ftOWHtthfWti
Screw fits into spring end.
Double hook
Dowel
Helix angle
Tab with 3 holes engages IY2 spring-coils.
Twin-spring setup includes double hook and triangular tab.
Two holes
Be sure edge is blunt
Tight fit for permanent support
Long tab with 2 holes in midsection provides ample adjustment. Sheetmetai, slit and formed, suspends spring.
Copyright © 2005 by The McGraw-Hill Companies
Cross-pin holds spring deep in hole.
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Countersink
Adjusting screw
Co py rig hte dM ate ria l
Groove
Setscrew.
Panel
Countersunk hole leaves spring free to turn.
Tension adjustment requires nonrotating screw.
COMPRESSION
SPRINGS
Fixed supports
Stop
Unsupported spring-body must have somewhat more resistance to buckling in fixed supports (9) than pivoted ones (10).
Supported springs are exemplified in push button (11) and friction clutch (12). Friction faces
Driven gear Adjusting collar
Pivoted supports Pinion gear
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Housing
Panel
Internal plug
Co py rig hte dM ate ria l
Movable Conical end
Dished bottom
Bushing
Double guidance is exemplified by hole-bottom that centers spring end, and internal plug that supports spring body.
Concealed spring is supported externally by closed-end bushing, which also determines amount of compression.
Tight-wound coils
Plug
Sliding coble,
Drilled vanes
Active length
Bushing
Covity
Tight-wound end-coils hold switchboard plug bushing—spring absorbs shock when weighted cable snaps entire assembly back into cavity after operator disconnects plug at end of message. FLAT
Adjustment vanes have holes that match spring pitch. Spring coils threaded through vanes become inactive, thus varying effective spring length.
TORSION-SPRINGS
Attachment slot
Notched end
Spring
Saw-cut slot retains spring positively if slot end is peened over or otherwise closed.
Copyright © 2005 by The McGraw-Hill Companies
Notched dowel provides hook for hole in spring end.
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Standord screw
Center-punch holes
Co py rig hte dM ate ria l
Drive fit
Chorda! shot in shaft is closed tight by displacing metal with center punch for permanent spring retention.
Headed drive-pin through spring hole makes disassembly difficult (19). Standard screw (20) eases disassembly. Chisel ted ears
Raised metal
Chordal groove holds spring when ears are formed by chiselling or staking after assembly.
Raised metal, produced by staking, provides low-cost yet firm hook on shaft.
Slotted spring-housing is simple, but spring-end can be dangerous if housing revolves and is unprotected.
Clearance hole for rivet head
Lanced tab avoids hazard of external spring-end but dirt can enter housing.
Shoulder rivet fastening.
provides dustproof
Slot in thin wail
Pin
Mounting plate
Mounting pin on plate may be plain/ or headed—for more positive spring retention.
Taper pin,
Mounting post'
Taper pin allows end adjustment of precision, lowtorque springs.
Copyright © 2005 by The McGraw-Hill Companies
Setscrew and slotted post also provides adjustment feature but may be inefficient if springend becomes dimpled.
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2 0
T a r n p e r - P r o o f
F a s t e n e r s
Ways to prevent or indicate unauthorized removal of fasteners in vending machines, instruments, radios, TV sets, and other units. Included are positively retained fasteners to prevent loss where retieval would be difficult.
Co py rig hte dM ate ria l
Federico Strasser
Wa x-filled recess
Cupped sleeve
Square cup
Pin
Wax
(A)
(B)
Fig, 1—(A) Wax or other suitable material fills recess above screw. Wax flush with plate hides screw position if surface is painted. (B) Cupped sleeve
(C)
riveted in screw hole provides cavity for wax when plate is too thin for recessing. (C) Pin prevents rotation of square cup which would allow screw to be removed without disturbing wax.
Lead sea/-
(A)
Leacf seaf-
(B)
Fig. 2—(A) Lead seal crimped over twisted ends of wire passing through screw allows only limited slackening of nut. (B) Two or more screws strung through
Groove
heads with wire are protected against unauthorized removal by only one seal. Code or other signet can be embossed on seals during crimping.
Pressure expands disk in groove Dig, of dished disk
Driving holes '
Driving faces
Left hand thread Dia. of expanded disk
Fig. 3—Sheet-metal disk pressed into groove can only be removed with difficulty and discourages tampering.
(A)
(B)
(O
Fig. 4—(A) Spanner-head screws are available in all standard heads and sizes from U.S. manufacturers. Special driver is required for each screw size except !-in. dia and above. (B) Left-hand screw thread is sometimes sufficient to prevent unauthorized loosening, or (C) special head lets screw be driven but not unscrewed.
Copyright © 2005 by The McGraw-Hill Companies
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POSITIVELY RETAINED FASTENERS
Co py rig hte dM ate ria l
Split ring
(A)
(8)
(C)
Fig. 5—(A) Tapped cover and casing allows screw (a > b) with reduced shank diameter to be completely unscrewed from casing yet retained positively in cover. For thin sheet-metal covers, split ring on reduced shank (B) is preferable. Snap ring in groove (C) or transverse pin (D) are effective on unreduced shank. Simple and cheap method (E) is fiber washer pushed over thread.
Pin
Snap ring
(Dl
Fiber washer
(E)
Tig. 6—Open-ended slot in sliding cover allows screw end to be staked or burred so screw cannot be removed, once assembled.
Staked screw
Staked end
SlQt in sliding cover
Binding-head screw
(A)
(B)
Riveted but free to move
(D)
Fig. 7—(A) Nut is retained on screw by staking or similar method but, If removal of nut is occasionally necessary, coaxial binding-head screw (B) can be used. Where screw end must be flush with nut, pin through nut tangential to undercut screw (C) limits nut movement. Rotatable nut (D) or screw (E) should have sufficient lateral freedom to accommodate slight differences in location when two or more screws are used.
Tangential pin
(O
(E) Spun or riveted over
Copyright © 2005 by The McGraw-Hill Companies
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L
a
n
F
a
s
c t
e e
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M e
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E l i m i n a t e s
S
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15 ways in which sheetmetal tabs, ears, and lugs can serve to fasten and locate.
Tab-
Co py rig hte dM ate ria l
Federico Strasser
Farce
Force
I
Slot
2
BENT-OVER TAB holds together up to four layers of sheetmetal. Designing tabs to stress in shear increases holding strength.
Tab
Wedge shape
4
3
TWISTED TAB is less common than bent one. Shaped tab wedges tightly when twisted.
Disc
Tube,
Tab
Disc.
Riveted tab end5
6
WITH THICK STOCK, end of tab can be riveted.
Tabs
7
THESE TABS both locate and hold disk in tubing. When necking locates disk, tab only holds—again by wedge action.
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Groove
9
8
Tube-
Bar
Tube
Co py rig hte dM ate ria l
Bar-
LIP AND TABS combine to join round bar and tubing. For longer bars, tabs fit into grooves. Bar can rotate inside tube if tabs are pressed lightly into groove.
Shelf
Rubber
Plastic
W
10
Sheet metal insert
12
Plastic-
METAL REINFORCEMENTS and mounting pads grip plastic better if lanced.
Spot weld
LANCED SHELL secures rubber in bumper or instrument foot.
Tubing
Bar
Braze
Tab
Slot
14
13
CORNER REINFORCEMENT grips wood, plastic or fiber with lanced teeth. Similarly, lanced nameplates or labels attach easily to equipment or instrument panels by pressing into the surface.
INTERLOCKING SLOT and tab
connects two pieces of tubing. Joint is permanent if inner tubing has thick wall. If inner tube has thin wall, tab can be depressed and tubes pulled apart if desired.
Copyright © 2005 by The McGraw-Hill Companies
15
LANCED FLAPS provide large contact areas for brazing or soldering sheetmetal fins to bars and pipes. An alternate method for round bars or pipe is an embossed collar around the hole. However, for angular shapes, flaps are easier to make.
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J o i n i n g i
t
h
o
u
t
F
a
s
t
e
n
P a r t s e
r
s
Co py rig hte dM ate ria l
w
C i r c u l a r
Fig. 1—Fastening for a rolled circular section. Tabs are integral with shoot; one tab being longer than the other, and bent over on assembly.
Fig. 5—Similar to Fig. 4 for supporting electrical wires. Tab is integral with plate and crimped over on assembly.
(A)
Fig. 6—For supporting of rods or tubes. Installation can be either permanent or temporary. Sheet metal bracket is held by bent tabs.
'B)
Fig. 10—Plate is embossed and tabs bent over on assembly. If two plates are used having tab edges (B) a piano-type hinge is formed. (A) and (B) can be combined to form a quick release door mechanism. A cable is passed through the eye of the hinge bolt, and a handle attached to the cable.
(A)
Fig. 7—Embossed shoot metal bracket to hold rods, tubes or cables. Tension is suppHcd b> screw threaded into lower plate.
Fig. 11—Rods and tubes can be supported by sheet metal tabs. Tab is wrapped around circular section and bent through plate.
(B)
Fig. 14—Strap fastener to hold a circular section tight against a structural shape. Lock can be made from square bar stock (A) or from sheet metal (B) tabbed as shown. Strap is bent over for additional locking. Slotted holes in sheet should be spaced equal to rod dia to prevent tearing.
Copyright © 2005 by The McGraw-Hill Companies
Fig. 15—C clamp support usually used for tubing. Serrated wedge is hammered light; serrations keep wedge from unlocking.
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Co py rig hte dM ate ria l
Fig. 2—Similar to Fig, 1 except tube is formed with a lap joint. Tab is bent over and inserted into cut-out on assembly. Joint tension is needed to maintain lock.
Fig. 3—Tab fastener for elliptical section. Tabs are formed integral with sheet. For best results tabs should be adjacent to each other as shown in sketch above.
(A)
Fig. 8—Fastening of rod to plate. Rod is welded to plate with slotted holes. Tabs in bottom plate are bent on assembly.
Fig. 4—For supporting rod on plate. Tab is formed and bent over rod on assembly. Wedging action holds rod in place. Rod is free to move unless restrained.
(B)
Fig. 9—Tabs and bracket (A) used to support rod at right angle to plate. Bracket can be welded to plate. (B) has rod slotted into place. For mass production, the tabs and slots can be stamped into the sheet. For limited production, the tabs and slots can be hand formed.
(A)
(B)
Fig. 12—For connecting wire ends to terminals. Sheet is crimped or tabbed to hold wire in place. Variety of terminal endings can be used. If additional fastening is required, in that parting of the wire and terminal end might create a safety or fire hazard, a drop of solder can be added.
(A) Fig. 16—Methods of locking rods in machine frames. In (A) one end of the rod is machined Io a smaller diameter. Shoulder and bent member restrains rod from slipping out of frame. Limited axial and rotational freedom is present*
Fig. 13—Spring joins two rods or tubes. Members are not limited in axial motion or rotation except by spring strength.
(B)
(C) Split rod in (B) limits axial motion but permits rotation. Rod is split on assembly. Wedge or pin in (C) bear against washers. Axial motion can be restricted but rotation is possible. If rod is to be a roller, bearings can be inserted.
Copyright © 2005 by The McGraw-Hill Companies
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
5
Co py rig hte dM ate ria l
LOCKING DEVICES & METHODS Frc ito i n Calmpn ig Devc ies Retan in ig and Lockn ig Detents How Sprn ig Calmps Hod l Workpeices Hod ln ig Fx iture for Workpeice 15 Ways to Fasten Gears to Shafts 8 Control Mounn itgs 8n I tero l ckn i g Sheetmetal Fasteners Fastenn ig Sheet-Metal Parts by Tongues, Snaps, or Cn ilchn ig Snap Fasteners for Poy lethye lne Snap Fasteners for Poy lstyrene
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
5-2 5-4 5-6 5-8 5-9
5-14 5-16 5-18 5-20 5-22
F r i c t i o n
C l a m p i n g
D e v i c e s
Bernard J. Wolfe
ALL TYPES of mechanisms used for gaining mechanical advantage have probably been used in the design of friction clamps. This type of clamp can hold moderately large loads by friction grip on smooth surfaces even of comparatively small area and, in some designs, tightened or released with little effort and movement of the control. In the clamps illustrated here the mechanical advantage is gained by the use of the common devices: lever, toggle, screw, wedge, and combinations of these means*
Co py rig hte dM ate ria l
Clamping skirt
Slide-
T~bott
Clamp screw. Cone tip lifts T'bolt to clamp slide to bed
Bed
SLIDE CLAMP
Cloimp screw draws shoe erne/ yoke together
S e c t i o n A-A
A
Revolving table
Clamping skirt
A
A
Stationary table
Clamp shoe
Clamp support
Clamp yoke
T U R N T A B L E CLAAAP Clamp assembly floats on pin and does no+ disturb table setting
Connecting rod-
A
Clamping yoke
Pulley
C
Pivot
Spindle
Tapered gib
Section B-B
stud
Spmdfe
Elongated
housing hole
Clamping lever
Feed screw B
Clamp stud
B Way gib -tfut tocknut Section A-A
C DOUBLE C L A M P FOR SPINDLE HEAD
Copyright © 2005 by The McGraw-Hill Companies
Elongated hole equalizes clamping arcfion
S e c t i o n C-C
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.
Clamping lever
Small handwheel rotates spurSleeve with gear to adjust center rack teeth Large handwheel operates damp blocks through long sfeeve
Support
Center is journafed in bearings within sleeve-
table or platform support 800 Ib:
Co py rig hte dM ate ria l
Spur gear
Shaf^
CENTER SUPPORT CLAMP
-Slide bed
Slide shaft
Cfamp spring Lock"
Cfamp yoke holds shafts in alignment
RIGHT ANGLE CLAMP
SLIDE CLAMP
A
Cfamp handfe tightens in fess than 30deg. turn
Specimen clamp screw
Clamp siud Sfucffock nut for fine adjustment
Tabfe
Cfamp support
Specimen holder has 30'deg. range
Clamp nut A
damping washer with sphericaf surface-
Base or pedestal
PEDESTAL CLAMP
Clamp stud tightens two shafts simultaneously
Horizontal Shaft
Specimen clamp
Clamp with finger release lever
Blocks clamp sleeve when pushed together
long sleeve
Vertical shaft
will
Clamping nut with outside threads
Section A-A Cfamp stud key prevents turning
Clamp teeth Cfamp
SPECIMEN HOLDER CLAMP
Copyright © 2005 by The McGraw-Hill Companies
Cfamp screw Frame TABLE CLAMP
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R e t a i n i n g L o c k i n g
a n d D e t e n t s
Many forms of detents are used for positioning gears, levers, belts, covers, and similar parts. Most of these embody some form of spring in varying degrees of tension, the working end of the detent being hardened to prevent wear.
Co py rig hte dM ate ria l
FiG. i
Adam Fredericks
B
A
Fig. 1—Driving plunger, shown in engagement at A is pulled out, and given a 90-deg. turn, pin X slipping into the shallow groove as shown at B, thus disengaging both members.
ICnurleot
FIG.4
X
A
Disengaged position
Fig. 4—The plunger is pinned to the knurled handle which is pulled out and twisted, the screw A dropping into the
locked position at X in the bayonet slot.
FIG. 2
Fig. 2—The pin in the collar attached to the p l u n g e r rides on the end of the handle when in the disengaged position and drops into the hole Y to allow engagement.
'•Engaged position
A
FIG.5
Fig. 3—A long and a short slotted pin driven into the casting gives two plunger positions.
Fig. 5—In this design, the pin A engaging in the slot prevents the plunger from turning. This detent is used as a temporary gear lock which is engaged for loosening a drawback rod through the gear.
Fig. 6—An adjustable gear case cover lock. Pushing the door shut, it is automatically latched, while pulling out the knurled knob A disengages the latch.
Knurled FIG.3
A
FlG. 6
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FIG.7 Fig. 7—In this design the plunger is retained by staking or spinning over the hole at A.
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Co py rig hte dM ate ria l FIG.IO
Fig. 10—Another form in vhich the grooves are cut all around the rod, which is then free to turn to any position.
B
A
A
B
B
FIG. 6
FIG.II
Fig. S—End of the plunger B bearing against the hand lever A is concaved and prevented from turning by the dog point setscrew engaging the splined slot. Friction is the only thing that holds the adjustable hand lever A in position.
FIG.9
Fig. 9—A spring-backed steel ball makes a cheap but efficient detent, the grooves in the rod having a long, easy riding angle. For economy, rejected or undersized balls can be purchased from manufacturers.
Figs. 11 and 12—Above is shown a doublelocking device for gear shift yoke rods. At A the neutral position is shown with ball X free in the hole. At B the lower rod is shifted, forcing ball X upwards, retaining the upper rod in a neutral position. The lower rod must also be in neutral position before the upper rod can be moved. To the right is shown a similar design wherein a rod with hemispherical ends is used in place of ball X.
FlG.12
B
A
FIG.13 Fig. 13—Without using a spring of any kind, three gear-shifting rods are locked by a large steel ball. At A, the neutral position is shown. At B, the lower rod has been shifted, forcing the ball upwards, thereby locking the other two rods. The dashed circle shows the position of the bail when the right-hand rod has been shifted.
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
H o w
S p r i n g
C l a m p s
H o l d
W o r k p i e c e s
Here's a review of ways in which spring clamp devices can help you get a grip on things.
Co py rig hte dM ate ria l
Federico Strasser
Counterweights optional
Slot
Workpiece
Movement
Workpiece
Compression spring
RODS OF DIFFERENT SECTION can be easily held by this device. Strength of grip can be varied if necessary.
SECOND-CLASS LEVER gives | 0 \v clamping forces for parts that are easily marked or require gentle handling.
Holding pin
Lid
Workpiece Locating hole (optional)
FLAT SPRING ACTS THROUGH PIN that holds the workpiece in the fixture. This device also positively locales parts.
Copyright © 2005 by The McGraw-Hill Companies
Fixed fulcrum
Bearing surface
Detachable fulcrum
COVER LATCH is an ideal application for spring and notched lever, Make the fulcrum detachable for ease of repair.
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Co py rig hte dM ate ria l
Drilling bushing
hlai springs
Flat spring.
Workpiece
Weld or rivet here
FLAT WORKPIECES of constant thickness are held with a couple of flat springs attached to the jig table.
Lid
Leaf spring
SIMPLE CLAMPING FIXTURE is ideal
for holding two flat pieces of material together for either welding or riveting.
Cutaway in box
Cutaway in Hd
Tension spring
LEAF-SPRING latch can be fashioned as shown, or the spring itself can be formed to provide its own latching notch.
Copyright © 2005 by The McGraw-Hill Companies
POSITIVE OPEN-OR-SHUT lid relies
upon a spring. Over-center spring action makes the lid a simple toggle.
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F i x t u r e
f o r
W o r k p i e c e
Co py rig hte dM ate ria l
H o l d i n g
Workpiece to be machined
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
1 5
W a y s
t o
F a s t e n
G e a r s
t o
S h a f t s
So you've designed or selected a good set of gears for your unit-now how do you fasten them to their shafts? Here's a roundup of methods-some old, some new-with a comparison table to help make the choice. L. M. Rich
PINNING
Co py rig hte dM ate ria l
1
Pinning of gears to shafts is still considered one of the most positive methods. Various types can be used: dowel, taper, grooved, roll pin or spiral pin. These pins cross through shaft (A) or are parallel (B). Latter method requires shoulder and retaining ring to prevent end play, but allows quick removal. Pin can be designed to shear when gear is overloaded.
Main drawbacks to pinning are: Pinning reduces the shaft crosssection; difficulty in reorienting the gear once it is pinned; problem of drilling the pin holes if gears are hardened.
Recommended practices are: • For good concentricity keep a maximum clearance of 0.0002 to 0.0003 in. between bore and shaft. • Use steel pins regardless of gear material. Hold gear in place on shaft by a setscrew during machining. •Pin dia should never be larger than i the shaft—recommended size is 0.20 D to 0.25 D. • Simplified formula for torque capacity T of a pinned gear is:
(A)
Shoulder
(B)
T -0.787 SdW
where S is safe shear stress and d is pin mean diameter.
Copyright © 2005 by The McGraw-Hill Companies
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Pin through shaft
Pin Retaining ring
2 CLAMPS AND COLLETS Hub clamp
Slotted hub
Hexagonal collet
Gear Shaft
Co py rig hte dM ate ria l
Split gear hub (A)
Slight clearance
Clamping is popular with instrument-gear users because these gears can be purchased or manufactured with clamptype hubs that are: machined integrally as part of the gear (A), or pressed into the gear bore. Gears are also available with a collet-hub assembly (B). Clamps can be obtained as a separate item. Clamps of one-piece construction can break under excessive clamping pressure; hence the preference for the two-piece clamp (C). This places the stress onto the screw threads which hold the clamp together, avoiding possible fracture of the clamp itself. Hub of the gear should be slotted into three or four equal segments, with a thin wall section to reduce the size of the clamp. Hard-
(C)
(B)
Clamp
ened gears can be suitably fastened with clamps, but hub of the gear should be slotted prior to hardening. Other recommendations are: Make gear hub approximately same length as for a pinned gear; slot through to the gear face at approximately 90° spacing. While clamps can fasten a gear on a splined shaft, results are best if both shaft and bore are smooth. If both splined, clamp then keeps gear from moving laterally. Material of clamp should be same as for the gear, especially in military equipment because of specifications on dissimilarity of metals. However, if weight is a factor, aluminum-alloy clamps are effective. Cost of the clamp and slitting the gear hub are relatively low.
Resulting tensile stress in the gear bore is:
where f = coefficient of friction (generally varies between 0.1 and 0.2 for small metal assemblies), D1 is shaft dia, D2 is OD of gear, L is gear width, e is press fit (difference in dimension between bore and shaft), and E is modulus of elasticity. Similar metals (usually stainless steel when used in instruments) are recommended to avoid difficulties arising from changes in temperature. Press-fit pressures between steel hub and shaft are shown in chart at right (from Marks' Handbook). Curves are also applicable to hollow shafts, providing d is not over 0.25 D.
Copyright © 2005 by The McGraw-Hill Companies
Unit pressure between steel hub and shaft
Allowonce per inch of shaft diamM e
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d/D
Press-fit gears to shafts when shafts are too small for keyways and where torque transmission is relatively low. Method is inexpensive but impractical where adjustments or disassemblies are expected. Torque capacity is:
Press-fit pressure between hub and shaft, Ib per sq in.
3 PRESS FITS
Reliability Under j Operation
Versatility in Applications
Ability to Meet Environment Specs
Machining Requirements
I Ability to Use Prehardened Parts
Relative Cost
M e t h o d s
Excellent Good Fair Good Fair Excellent Excellent Good Excellent Poor Poor Excellent Good Excellent Good
Poor Excellent Fair Good Excellent Excellent Poor Poor Excellent Fair Excellent Excellent Excellent Excellent Poor
Excellent Fair Good Good Poor Excellent Excellent Good Excellent Poor Good Excellent Good Excellent Good
Excellent Fair Fair Excellent Good Fair Good Poor Poor Poor Fair Good Excellent Good Excellent
Excellent Good Good Excellent Fair Excellent Excellent Good Excellent Good Good Excellent Good Good Good
High Moderate Moderate Little Moderate High High Moderate High Moderate Moderate High Moderate Moderate Little
Poor Excellent Excellent Excellent Good Excellent Excellent Poor Excellent Poor Excellent Excellent Excellent Excellent Fair
High Medium Medfum Low low High High Medium High Low Medium High Medium High Low
Co py rig hte dM ate ria l
Pinning Clamping Press fits Loctite Sets c re ws Splining Integral shaft Knurling Keying Staking Spring washer Tapered shaft Tapered rings Tapered bushing Die-cast assembly
Gear-Fastering i Ease of Replacing Gear
Method
of
Torque Capacity
C o m p a r i s o n
4 RETAINING
COMPOUNDS
Several different compounds can fasten the gear onto the shaft—one in particular is "Loctite/' manufactured by American Sealants Co. This material remains liquid as long as it is exposed to air7 but hardens when confined between closely fitting metal parts, such as with close fits of bolts threaded into nuts. (Military spec MIL-S-40083 approves the use of retaining compounds). Loctite sealant is supplied in several grades of shear strength. The grade, coupled with the contact area, determines the torque that can be transmitted. For example: with a gear 1 in. long on a &-in.-dia shaft, the bonded area is 0.22 in.2 Using Loctite A with a shear strength
of 1000 psi, the retaining force is 20 in.-lb. Loctite will wick into a space OX)OOl in. or less and fill a clearance up to 0.010 in. It requires about 6 hr to harden, 10 min. with activator or 2 min. if heat id applied. Sometimes a setscrew in the hub is needed to position the gear accurately and permanently until the sealant has been completely cured. Gears can be easily removed from a shaft or adjusted on the shaft by forcibly breaking the bond and then reapplying the sealant after the new position is determined. It will hold any metal to any other metal. Cost is low in comparison to other methods because extra machining and tolerances can be eased. 6 GEARS INTEGRAL W I T H SHAFT
5 Setscrews
Fabricating a gear and shaft from the same material is sometimes economical with small gears where cost of machining shaft from OD of gear is not prohibitive. Method is also used when die-cast blanks are feasible or when space limitations are severe and there is no room for gear hubs. No limit to the amount of torque which can be resisted—usually gear teeth will shear before any other damage takes place.
Two setscrews at 90° or 120° to each other are usually sufficient to hold a gear firmly to a shaft. More security results with a flat on the shaft, which prevents the shaft from being marred. Flats give added torque capacity and are helpful for frequent disassembly. Sealants applied on setscrews prevent loosening during vibration.
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4-spline D
w
V2
0.120
0.125
/4
0.181
0.188
7
0.211
0.219
I
i 0.241
0.250
0.301
0.313
1-V4
Co py rig hte dM ate ria l
Ideal where gear must slide in lateral direction during rotation. Square splines often used, but involute splines are self-centering and stronger. Nonsliding gears are pinned or held by threaded nut or retaining ring.
Torque strength is high and dependent on number of splines employed. Use these recommended dimensions for width of square tooth for 4-spline and 6-spline systems; al-
8
KNURLING
9
KEYING
though other spline systems are some times used. Stainless steel shafts and gears are recommended. Avoid dissimilar metals or aluminum. Relative cost is high.
A knurled shaft can be pressed into the gear bore, to do its own broaching, thus keying itself into a close-fitting hole. This avoids need for supplementary locking device such as lock rings and threaded nuts. The method is applied to shafts i in. or under and does not weaken or distort parts by the machining of groove or holes. It is inexpensive and requires no extra parts. Knurling increases shaft dia by 0.002 to 0.005 in. It is recommended that a chip groove be cut at the trailing edge of the knurl. Tight tolerances on shaft and bore dia are not needed unless good concentricity is a requirement The unit can be designed to slip under a specific loadhence acting as a safety device.
(A)
Generally employed with large gears, but occasionally considered for small gears in instruments. Feather key (A) allows axial movement but keying must be milled to end of shaft. For blind key way (B), use setscrew against the key, but method permits locating the gear anywhere along length of shaft. Keyed gears can withstand high torque, much more than the pinned or knurled shaft and, at times, more than the splined shafts because the key extends well into both
w
3
/8
7 S P L l N E D SHAFTS
6- spline
(B)
the shaft and gear bore. Torque capacity is comparable with that of the integral gear and shaft. Maintenance is easy because the key can be removed while the gear remains in the system. Materials for gear, shaft and key should be similar preferably steel. Larger gears can be either cast or forged and the key either hot- or cold-rolled steel. However, in instrument gears, stainless steel is required for most applications. Avoid aluminum gears and keys.
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1 1 SPRING WASHER
1 0 STAKING %fts
Clearance ff%»
4
0.0/5
0.0020
27
4
0.0/5
0.0025
20
4
0.020 0.0020
28
4
0.020
30
0.0020
.Gear*
Co py rig hte dM ate ria l
clearance
(4)stake- equally spaced Depth of stake
D*h
8
0.020
O
52
Gear Hub
It is difficult to predict the strength of a staked joint—but it is a quick and economical method when the gear is positioned at the end of the shaft. Results from five tests we made on gears staked on 0.375-in. hubs are shown here with typical notations for specifying staking on an assembly drawing. Staking was done with a 0.062-in. punch having a 15° bevel. Variables in the test were: depth of stake, number of stakes, and clearance between hub and gear. Breakaway torque ranged from 20 to 52 in.-Ib. Replacing a gear is not simple with this method because the shaft is mutirated by the staking. But production costs are low.
12 TAPERED SHAFT
15 DIE-CAST
Assembly consists of locknut, spring washer, flat washer and gear. The locknut is adjusted to apply a predetermined retaining force to the gear. This permits the gear to slip when overloaded—hence avoiding gear breakage or protecting the drive motor from overheating. Construction is simple and costs less than if a slip clutch is employed. Popular in breadboard models.
13 TAPERED RINGS Spacer
Tapered shaft and matching taper in gear bore need key to provide high torque resistance, and threaded nut to tighten gear onto taper. Expensive but suitable for larger gear applications where rigidity, concentricity and easy disassembly are important. A larger clia shaft is needed than with other methods. Space can be problem because of protruding threaded end. Keep nut tight.
flat washer. •Spring washer Locknut
Tapered rings
These interlock and expand when tightened to lock gear on shaft. A purchased item, the rings are quick and easy to use, and do not need close tolerance on bore or shaft. No special machining is required and torque capacity is fairly high. If lock washer is employed, the gear can be adjusted to slip at predetermined torque.
14 TAPERED BUSHINGS
This, too, is a purchased item— but generally restricted to shaft diameters i in. and over. Adapters available for untapered bores of gears. Unthreaded half-holes in bushing align with threaded half-holes in gear bore. Screw pulls bushing into bore, also prevents rotational slippage of gear under load.
HUB
Die-casting machines are available, which automatically assemble and position gear on shaft, then die-cast a metal hub on both sides of gear for retention. Method can replace staked assembly. Gears are fed by hopper, shafts by magazine. Method maintains good tolerances on gear wobble, concentricity and location. For high-production applications. Costs are low once dies are made.
Copyright © 2005 by The McGraw-Hill Companies
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8
C o n t r o l
M o u n t i n g s
When designing control panels follow this 8-point guide and check for...
Co py rig hte dM ate ria l
Frank William Wood, Jr.
Grommei
Boot
. . . LOCKING. Control will stay fixed in spite of vibration or attempts to force shaft too far. Washer at right has two tabs; one fits in the panel, the other in the control bushing. Left washer has a boss which fits into a cutout in the panel and around a pin projecting from the control body.
. . . SEALING against dust or water. Boot seals between shaft and bushing and between bushing and panel. With control behind panel rubber grommet seals only one place.
Brush
Too close
In su IG ted\ coupling
. . . HAND-ROOM at front of the panel. Space knobs at least one inch apart. Extending knob to save space puts it where the operator can bump into it and bend the shaft. Best rule is to keep shaft as short as possible.
Copyright © 2005 by The McGraw-Hill Companies
. . . "HOT" CONTROL KNOBS. One approach is to ground them by installing a brush against the shaft. Another solution is to isolate the control by an insulated coupling or a plastic knob having recessed holding screws.
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Broken warning light
Co py rig hte dM ate ria l
Vernier coupling
. . . RESETTING to match controls to panel markings. For crude adjustments a set-screw is enough. Where matching is critical a threepiece vernier coupling permits more accurate calibration.
...ACCESSIBILITY behind the panel. Easy access reduces down time and maintenance costs especially if one man can do most jobs alone. Here, technician can't replace a warning light without dismantling other parts.
Raised position
Grooved knob
Support bracket
Collar
. . . LIMIT STOPS that are strong enough not Jo bend under heavy-handed use. Otherwise setting will change when stop moves. Collar and grooved knob permit adjustment; tab on bracket doesn't.
Copyright © 2005 by The McGraw-Hill Companies
. . . GUARDS to prevent accidental actuation of switches. Bell-shape guard for pushbuttons is just finger-size. U-shape guard separates closely spaced toggle switches, and a swinging guard holds down special ones.
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8
I n t e r l o c k i n g
S h e e t m e t a l
F a s t e n e r s
These eight sheetmetal parts join sheetmetal quickly with the simplest of tools, few screws or bolts.
Co py rig hte dM ate ria l
L. Kasper
SQUEEZE CLIP holds two overlapping sheets, together. The, ends of the clip are, pushed through parallel slots, then bent over much like a staple.
ALIGNING PIECE slides up out of the way in longslQt while hutting sheets are being positioned. Afterwards it slips down over lower sheet.
ESS supports shelf between uprights, By1 mating vfith nptcneo^edgeiracts as a fcey to keep shelf fj-ont sOdipg jbaejk ajnd foftlri ana* provides positive location,1
CUP carries a bar on both sides of divider. Here bars: $tick up above the top, but deeper cutout will lower them until theyf are flush or sunk. \
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l BRACKETS provide instantly mobile rack space for boxes. To install or remove, squeeze sides together and push hooked ends through slots.
FLANGE HOLDER does double duty by holding up shelves on both sides of a partition. Angular corners allow it to fit through small slit when tilted.
CLAW holds top sheet between two end pieces. Tail snaps into slot, then claw is hammered over edge. With notched edge, top is even with sides.
BAR clamps divider in place. Extruded holes provide a recess for screws so that they stay flush with upper surface of horizontal sheet.
Copyright © 2005 by The McGraw-Hill Companies
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F a s t e n i n g S n a p s ,
o r
S h e e t - M e t a l
P a r t s
b y
T o n g u e s ,
C l i n c h i n g
Co py rig hte dM ate ria l
Detachable and permanent assembly of sheet metal parts without using rivets, bolts, or screws.
Fig* 1—Supporting bracket formed from sheet metal and having integral tabs. Upper tab is inserted into structure and bent. Ledge weight holds lower tab.
Fig. 2—Supporting bracket similar to Fig. 1 but offering restraint to shelf or ledge. Tabs are integral with sheet metal part and are bent on assembly.
Fig. 3—Supporting ledge or shelf by direct attachment. Tab is integral and bent on assembly. Additional support is possible if sheet is placed on flange and tabbed.
Fig. 7—'Box section joined to a flat sheet or plate. Elongated holes are integral with box section and tabs are integral with plate. Design is not limited to edge location.
Fig. 8—Bar is joined to sheet metal bracket by a pin or rod. Right angle bends in pin restrict sidewise or rocking motion or bar. Bracket end of pin is peened.
Fig. 9—To support and join sheet metal support at right angle to plate. Motion is restricted in all directions. Bottom surface can be grooved for tabs.
Fig. 13—A spacing method that can be used for circular sections. Formed sheet metal member support outer structure at set distance. Bead centers structure.
Fig. 14—A removable section held in place by elasticity of material. Design shown is a temporary or a removable cover for an elongated slotted hole in a sheet metal part.
Fig. 15—A cover held in position by bead and formed sheet. Cover is restrained from motion but can be rotated. Used for covers that must be removable.
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Co py rig hte dM ate ria l
Pig. 4—To support or join a flat sheet metal form on a large plate. Tabs are integral with plate and bent over on assembly. Only sidewise motion is restricted.
Pi g . 5—Similar to Fig. 4 but motion is restricted in all directions. Upper sheet is slotted, and tabs are bent over and into slots on assembly.
Pig. 6—Single tab design for complete restriction of motion. Upper plate has an elongated hole that matches width and thickness of integral lower plate tab.
Fig. 10—Channel section spot welded to plate forms bottom surface and joins box section to plate. Channel edges can be crimped or spot welded to restrict motion.
pig. 11—Sheet metal strap used to join two flat surfaces. Edges of plate are rounded to allow strap to follow contour and prevent cutting of plate by the metal strap.
pi g i 12—Sheet metal structures can be spaced and joined by use of a tabbed block. Formed sheet metal U section is held to form by the block as shown.
(B)
(A)
(A)
(B)
Fig. 16—A non-removable cover design. The vessel is notched as shown in A, and the cover crimped over, B, on assembly. This is a permanent cover assembly.
(D)
(E)
(C)
[F)
Fig. 17—S ix methods of joining two sheet metal parts These can be torn porary or permanent joints. If necessary, joints TrewTd or welded for added strength and suppo can be riveted, bolted, used to make right angle corner joints on sheet rt. Such jo.nts can also be metal boxes, or for attaching top and bottom covers on sheet metal containers.
Copyright © 2005 by The McGraw-Hill Companies
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S n a p
F a s t e n e r s
f o r
P o l y e t h y l e n e
It's difficult to cement polyethylene parts together, so eliminate extra cost of separate fasteners with these snap-together designs. Edger Burns
Co py rig hte dM ate ria l
Porting fine Ejector pin
Parallel P. L
Round hole
RL.
Female snap
(a) Cored hole
Hole tormed by "shutting off" the^ mold cavity
Vertical PL
Rectangular hole
RL
RL
WALL-END SNAP is easier to remove from the mold than the ejector-pin snap. The best length for this snap is VA to V2 in.
(b) "Shut-off" hole for female snap for different RL.
EJECTOR-PIN of mold is cut to shape of snap. Ejected with the pin, the part is slid off the pin by the operator.
As large as possible - to reduce tearing or permanent deformation
Female snap
Romps
RL,
Male snap
Open snap OPEN SNAP relies on an undercut in the mold and on the ability of the polyethylene to deform and then spring back on ejection.
Copyright © 2005 by The McGraw-Hill Companies
T SNAP locks with a 90-deg turn. To prevent this snap from working loose, four small ramps are added to the female part.
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Co py rig hte dM ate ria l Female snap
Mole snap
Expanding segements"
Round snap
Female snap
Spear snap
SPEAR AND ROUND snaps arc similar in design to the wall-end snap, but are ideal for assembling small parts to larger ones.
SEGMENTED WALL of female snap allows a large-headed male snap to enter easily. The snap can not be pulled apart with light loads. Core holes letsnaps be molded
RL
RL
Female locator
Aligning dio.
Support ribs
Male locator
RL RL
Female locator
ROTATING parts can be snapped securely together with three (shown) or two snaps. Mostly for linear polyethylene, it's strong.
Copyright © 2005 by The McGraw-Hill Companies
LOCATORS are not really snaps, hut align parts for subsequent eyeleting or riveting or in conjunction with other snaps.
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RL
S n a p
F a s t e n e r s
f o r
P o l y s t y r e n e
Here's a low-cost way to join injection-molded polystyrene parts without the use of separate fasteners or solvents.
Co py rig hte dM ate ria l
Edger Burns
Male port
Wall
PL Pin (usually 78-in. dia. for 1 Ai-In: to 3/8~in. length)
No draft-
Ejector pin ~3/32-in. dia. allows for small radius
Curved gripping sections provide more contact area with male port
Male half
No draft
Radius
No draff
Draff
Draft
RL
RL
Female half
Female part
CEMENTING SNAP will allow solvent cementing between the male and female members if required, although the snap will hold well without cement. Usually two or more such snaps are positioned around the parts to be joined. Male part is virtually the same as for the triangular snap. Blind, cored hole requires no shutoff.
TRIANGULAR SNAPS actually depend upon friction, but are strong and easy to assemble. Space several around the parts to be joined. Grip can also be adjusted to suit.
Female half
Shut-off hole
'A
Cored hole.
Section A-A
Male half
RL male port
RL femole port
A
BOX SNAP requires a mold shutoff in the female half, large enough to accommodate the male part, which slips behind a shoulder and locks, as shown in the diagram.
Copyright © 2005 by The McGraw-Hill Companies
DETENT SNAPS are ideal whenever a snap has to be frequently undone, and Where a tight hold is not required. The detent itself can be a hemispherical bump, or a more elongated shape.
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Co py rig hte dM ate ria l Male part
RL. could be here also
Shaft
Female part
Thicker section of snap allows undercut as tips stay softer for ejection
Assembly
RL
Undercut (0.015In. on snap dia. of tyglnj
B
RL
Female part
OPEN SNAPS have undercuts of about 0.015 in. on a total snap dia of Ys in. Despite small undercuts, stiff polystyrene gives good grip. This snap is not suitable for the regular nonimpact polystyrene. If the parting line can be arranged to lie in the other plane, as shown in B, ejection from the mold would be trouble free, thus avoiding excessive scrap.
PRONG SNAPS are ideal for snapping small parts onto a larger assembly. The male member is usually on the small part. Slot length in the female part must be designed for maximum holding power, without cracking the prongs on the male member.
Mole port
Female part
Undercut hook snap
Male part
Core
RL.
Shutoff
RL
Parting-line hook
HOOK SNAPS. Undercut hook snap relies on an undercut in the mold. To prevent polystyrene breakage on ejection front the mold, make the hooks thicker than the other parts — they then retain more heat, stay softer. Since large undercuts cannot be made this way, however, this snap loosens quite easily. Parting-line hook is much simpler to apply and is easier to design. Choose this snap whenever the part-
Cored hook ing line can be arranged to be in the plane shown on the drawing. It can be almost any strength and shape desired, and is simple to cut into the mold. Cored hook requires a core to come down from the other half of the mold, which then produces the inside of the snap. This will leave a hole in the wall to which the hook is attached. Three shutoff surfaces are also required in the mold construction.
Copyright © 2005 by The McGraw-Hill Companies
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
6
Co py rig hte dM ate ria l
GEARS & GEARING 6-2 Nomencalu tre of Gears Graphc i Representao tin of Gear Dm i enso ins 6-4 Worksheet Streamn iles Beve-G l ear Cac lua lto ins 6-6 Ag ilnment Chart for Face Gears 6-8 Power Capacty i of Spur Gears 6-10 Ln iear to Angua lr Converso in of GearT -ooh t n Idex Eror 6-13 Checks ilt for Pa lnetary-Gear Sets 6-14 Epc iycc il Gear Tran is 6-16 Cyco ld i Gear Mechansims 6-18 CardanG - ear Mechansims 6-25 Typc ial Meh tods of Provd in ig Lubrc iato in for Gear Syse tms 6-27
Copyright © 2005 by The McGraw-Hill Companies
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N o m e n c l a t u r e
o f
G e a r s
LINE Of CENTERS
SPUR & HELICAL GEARS
PITCH CIRCLE OUTSIDE DIA-(Dc)
Co py rig hte dM ate ria l
BASE CIRCLE
WORKING OEPTH(KK)
-TOOTH FILLET
CIRCULAR THICKNESS(t)
ARCQf ACTIO1N
CLEARANCE CO
PRESSURE ANGLE(j2f)
TOP LAND ADDENDUM^ PITCH POINT
TOOTH PROFILE
WHOLE DEPTH(Kt) CIRCULAR PITCH(P)
MOUNTING DISTANCE
CONE CENTER OR PITCH APEX
DEDENDUM(V)
LENGTH OFACTiON
PITCH APEX TO CROWN
CROWN TO BACK
CROWN POINT
BACK ANGLE
FACE ANGLE
ROOT ANGLE,
PINION
OUTSIDE DIA.,
№L\
FACE WIDTH F
GEAR
PITCH
C IAMETER1 D
LOCATING SURFACE BACK CONE'
BEVEL GEARS
Copyright © 2005 by The McGraw-Hill Companies
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PINION
GEAR
RACK
Co py rig hte dM ate ria l
LEFT-HAND HELICALTOOTH
RIGHT-HAND HELICAL TOOTH
SPUR GEARS
CROSSED HELICAL GEARS
PARALLEL HELICAL GEARS
WORM
WORM GEAR
SINGLEHELICAL GEARS
WORM
DOUBLE-HELICAL (HERRINGBONE) GEARS
HELICAL RACK
WORM GEARS
HOURGLASS WORM
PINION
SHAFT ANGLE
GEAR
BEVEL GEARS
MITER GEARS
ANGULAR BEVEL GEARS
90° +
CROWN GEAR
Adapted from: The New American Machinist's Handbook, © 1955 McGraw-Hill Copyright © 2005 by The McGraw-Hill Companies
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G r a p h i c a l o f
G e a r
R e p r e s e n t a t i o n D i m e n s i o n s
CIRCULAR THICKNESS, t
PITCH CIRCLE
Co py rig hte dM ate ria l
PRESSURE ANGLE,^
TOOTH PROFILE
CHORDAL ADDENDUM,ac
RADIAL LINE
BASECIRCLE
BASE CIRCULAR THICKNESS,tb
PITCH CIRCLE
NORMAL CIRCULAR, THK.,tn,
CHORDAL THICKNESS, t c
NORMAL ADDENDUM,*^
AXIAL THICKNESS,**
NORMAL CIRCULAR THK M tn
TRANSVERSE CIRCULAR THICKNES5,t t
NORMAL CHORDAL THICKNESS,t n c
EQUIVALENT PITCH RADIUS
SECTION: PLANE N O R M A L TO HELIX or SPIRAL at TOOTH CENTER
SECTION: PITCH SURFACES
TOOTH HELIX
LEAD.i
HELIX ANGLE, f
AXIS
LEAD ANGLE, X
LONG & SHORT A D D E N D U M TEETH
Copyright © 2005 by The McGraw-Hill Companies
EQUALADDENDUMTEETH
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PITCH WORKING DEPTH WORKING DEPTH,hK
ADDENDUM-
Co py rig hte dM ate ria l
WHOLE DEPTH*
DEDENDUM
CLEARANCE
WHOLE
CLEARANCES DEPTH7Ht
TOOTH T H I C K N E S S
ADDENDUM,^
PRESSURE ANGLE
DEDENDUM,b
BASIC
GEAR
W O R M
D0
GEAR
O U T S I D E DIA.,PQ
OUTSIDE DIAMETER,
THROAT DIAMETER,Dt
PITCH
RACK
PITCH DIAMETER, D
ROOT D I A M E T E R , D R
TRANSVERSE CIRCULAR PITCH,Pt
CIRCLE
AXIS
BACKLASH,B
FILLET RADIUS/r
AXIAL PITCH,
PROFILE RADIUS QF CURVATURE, P b BACKLASH
N O R M A L C I R C U L A R P I T C H , Ph
HELICAL
GEAR
Adapted from: The New American Machinist's Handbook, © 1955 McGraw-Hill Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Px
W o r k s h e e t
S t r e a m l i n e s
B e v e l - G e a r
C a l c u l a t i o n s B. J. Mumken
I he following worksheet neatly gathers together the many mathematical problems that need solving when designing straight bevel-gears. And they are numbered in the correct sequence—no need to hunt "all over the place" as when using formulas in the usual bevel-gear tables. In fact, there are no formulas as such—and, therefore, no need for working with the many Greek symbols found in them. Instead, the language here is in terms of the actual working operations. For example, space (9) tells you to obtain pitch diameter of the pinion—simply divide
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!
the value in space (1) by the value in space (3). And to get root angle for the gear, you are told to subtract the value in space (24) from the value in space (14). Each bracketed number refers you to a value previously filled in. Just fill in the known values for pinion and gear in the first eight spaces, then work through the sheet, which is based on the Gleason system for 90° straight bevelgears. Final result (next page) is gear-blank dimensions. Colored numbers show values obtained in a sample problem worked out by this method.
¥0
No. of teeth, pinion
Working depth=
5
,
2
0.100
ffi°
2
No. of teeth, geor
XO
6
Whole depth = ~~~ + 0.002 ("D + F") <3>
3
Diometrol pitch
IO
7
Pressure angle
4
Face width
0.1SO
8
Total backlash
9
£0°
0.003
P I N I O N GEAR (Thick underlining indicates working dimensions) (2) V. 000 IO Pitch dia. j-jj
Pitch dio. [^y
Il
O. XXO 8
0.50 OO
13
Pitch angle (N)1 in deg.
15
2 X cos (13)
17
Addendum (5) -(17)
U"'39'
2. 000
Z.0000
!2
14
Pitch angle (12)
/.7888
16
Cone distance jj^J
0.I3S
18
Addendum =
Stable)
0.0 & 5*
Gear Addendum for \ D. P. Ratio = (No. of gear teeth)/(No. of pinion teeth)
Ratios
To
Addendum, in.
From
LOO 1.00 1.02 1.03 1.05
LOO 1.02 1.03 1.05 1.06
0.850 0.840 0.830 0.820 0.810
1.06 1.06 1.09 L! I L13
1.08 1.09 1.1! 1.13 1.15
0.800 0.790 0.780 0770 0.760
From
Ratios
To
Addendum, in.
Ratios
From
To
1.15 1:17 1.19 1.21 1,23
LIT 1.19 1.21 1.23 1.26
0750 0740 0730 0720 0710
1.41 1.44 1.48 1.52 1.57
1.26 1.28 1.31 !.34 1.37
1.28 1.31 1.34 L37 1.41
0700 0.690 0.680 0.670 0.660
1.63 1.68 1.75 1.82 1.90
19
Dedendum = ^ p - 0 8 )
0.0X38
20
21
**
0.0121
22
23
Ded angle (21)
25
Face angle (13) + (24)
27
Root angle (13) -(23)
Hf,
24 2.8°
31' 26 28
From
To
Addendum, in.
1.44 1.48 1.52 1.57 1.63
Addendum, in. 0.650 0.640 0.630 0.620 0.610
Ratios
1.99 2.10 2.23 2.38 2.58
2.10 2.23 2.38 2.58 2.82
0.550 0.540 0.530 0520 0.510
1.68 1.75 1.82 1.90 1.99
0.600 Q590 0.580 0.570 0.560
2.82 3.17 3.67 4.56 7.00
3.17 3.67 4.56 7.00 a:
0.500 0.490 0.480 0.470 0.460
Dedendum= ^ | p — 0 7 )
O./S3 ^ O. O 3 H3
Ded angle (22) Face angle (14) +(23) Root angle (14) -(24)
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I"
SZ'
f/f
30'
cos (13)
o.$m
30
cos (14)
o.nm
31
[2 Jt (18)] x (29)
O.XHH
32
[2 K (I7)J x (30)
O.O5SI
33
OD= (9) +• (31)
f.XHff
34
OD- (IO) + (32)
$.058 (
35
0.0603
36
3.?3? 6
38
(I7) x (29) Pitch-apex to crown = [0.5 x (9)]- (36)
0.05 SI
37
(18) x (30) Pitch-apex to crown = [O.5x(IO)]-(35)
39
Ctrculor pitch = -r^j—
0.3/W
40
(I8)-(I7)
0.0700
4]
0.5 x (39)
OJ 570
42
(4I) x tan (7)
0.025H
43
Circular tooth thickness = (39)-(43)
0JZZ5'
44
Circular tooth thickness = (40H42)
0.13 i%
0.0OG O
46
(44)3
0.00IX
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29
3
L9H/1
45
(44)
47
2
(9)
ICOOOO
48
(!O)2
GH. OOOO
49
6x(47)
%. 0000
50
51
0.0000b
52
OJBf
54
6 x (48) (46) (50) Chordol tooth thickness = (43)-(52)-[0.5x(8)]
3V1000
(45) (49) Chordol tooth thickness = (44)-(5lK[0.5x (8)]
53
2
2
0.0000 0J30f
56
(43) x (30)
58
4 x (IO)
0.001*1
60
0.13 Gl
62
(56) (55) Chordal addendum (17) t (60)
0.0G5X
8735 64
sin (27)
O.H77!
66
cos (27)
0.8788
55
(44) x (29)
57
4 x (9)
59
61
(55) (57) Chordal addendum (18) + (59)
63
sin (28)
0
65
cos {28}
0.H776
0.03.18
/6.0000
PlIMlOlN
0.0077 3Z00 OO O.OO OX
GEAR
71
(16) - ( 4 ) (16)
72
(18) x (71)
0.6581 68 0.3583 70 0.832,3 OJlXH 73
74
(19) x (711
00617
75
(20) x (71)
OJXS O
76
[(72)t(74)] x (30)
0.0SI5
77
[(73)t(75i] x (29)
OJGZf
78
(33) - [ 2 x (69)]
3.5XH?
79
(34) - [ 2 x (70)]
6.73W
80
(76) + mfg. std.
0.1X5
81
(77) tmfg. std.
GKX 50
67
(4)x(63)
69
(4) x ( 6 5 )
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(4} x ( 6 4 )
(17) x (71)
0.05Hl
(4) x ( 6 6 )
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0.357? 0.6StI
A l i g n m e n t
C h a r t
f o r
F a c e
G e a r s
B. Bloomfield
for face gears is that diameter at which the teeth become pointed. The limiting inside diameter is the value at which tooth trimming occurs. This is always larger than the diameter for which the
operating pressure angle is 2ero. The two alignment charts that follow can be used to find the maximum OD and the minimum ID if the numbers of teeth in the face gear and pinion are known. They eliminate lengthy calculations.
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THE MAXIMUM PRACTICAL DIAMETER
CHART I
Pinion
No. "Teeth j Pin/on
No.Teeth, Face Gear
Face gear-
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Outside Diameter Factor
Outside dia Face Inside diet width
larger. Smaller ratios require pinion modifications not allowed for in these data. For both charts, the appropriate face gear diameter is found by dividing the factor from the chart by the diametral pitch of the pinion.
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FOR BOTH CHARTS the pinions are assumed to be spur gears of standard AGMA proportions, and the axes of the face gear and pinion are assumed to intersect at right angles. Both should be used only for tooth ratios of 1.5 to 1 or
Example:
Find the maximum outside diameter and the minimum inside diameter of afacegear with 70tedh that will mate with a 20toothstandard pinion whose pressure angle is 20 degrees and whose diameM pitch is 32 Solution: FfomCharfI: Outside Diameterfactors« S/ Max/mum OO -J§r ~ 2£3?H from Chart U; inside Diameterfactor..—-66.9m. Minimum /D**~& = 2.090 in.
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No.Teeth, Face Gear
No.Teeth, Pinion
Inside Diameter Factor
CHARTH
P o w e r
C a p a c i t y
o f
S p u r
G e a r s
Charles Tiplitz
that can safely be transmitted by a gear depends upon whether it runs for short periods or continuously. Capacity may be based on tooth strength if the gear is run only periodically; durability or wear governs rated horsepower for continuous running. Checking strength and surface durability of gears
can be a lengthy procedure. The following charts simplify the work and give values accurate to 5 to 10%. They are based on AGMA standards for strength and durability of spur gears.
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MAXIMUM RATED HORSEPOWER
Strength Nomograph is used first. Apart from the
Strength of Spur Gears. Based on AGMA 220.01 Oiometrol Circular pitch pitch
Pitch dia.-in.
rpm.
N (Teeth)
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Face width-in.
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X
Durability nomograph must be entered on scale X at the same value that was cut on the X scale on the strength chart. Both pinion and gear should be checked if made of different materials and the smaller of the values obtained should be used.
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usual design constants only two of the following three need be known: pitch, number of teeth and pitch diameter. To use the charts connect the two known factors by a straight line, cutting the third scale. From this point on the scale continue drawing straight lines through known factors, cutting the pivot scales. Between the double pivot scales the line should be drawn parallel to the adjacent lines.
Strength of Spur Gears (cont*) X
Rated horsepower
Pe a K horsepower
Pivot scale
Pivot scale
Dio metra 1 pitch
Tooth
Materio) strength
Steel
form factor Pressure angle No. of tooth
Service factor
Cast iron
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Service
and shock (Enclosed gearing } 8-(O HR NO
JL
N O S H OCK
•
M
-
H
O
E
O
A
.
V
Y
Material tactor
Pivot line
Gearratio factor
Pivot line Peak horsepower
Pitch dia.-in.
Steel BHN -J GEAR rPlNION
Gear ratio
MAX LADDEND. STD 1 ADDENO-
Tooth form factor Pressure angle
Rated horsepower
RPAVTf HEAVY ^= MOD CHOCK SH0CK
Service factor Service and shock (Enclosed gearing) 8-IOhr24hr day day
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Pivot line
Surface Durability of Spur Gears. Based on AGMA 210.01
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L i n e a r o f
t o
A n g u l a r
G e a r - T o o t h
I n d e x
C o n v e r s i o n E r r o r
For pitch diameters up to 200 inch, chart quickly converts index error from ten-thousandths of an inch to seconds or arc.
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Harold R. Ronan, Jr.
Pitch dta, in.
index error, in.
A-scale (for O to 100 in dta)
EXAMPLES = 1 Pitch dia of gear= 141 in. index error^O.OOl in. Read error converted to 3 sec on scale B 2. Pitch dia=4i in. Index error-O.OOl in. Read error converted to 10 sec on scale A
B-scale (for 100 to 200 in dio)
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C h e c k l i s t
f o r
P l a n e t a r y - G e a r
S e t s
These five tests quickly tell whether the gears will mesh, and whether there is room for them to fit together.
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Hugh R Hubbard
SYMBOLS
Circular pitch, in. Distance from center of sun gear to center of planet gear, in. Major or outside diameter of gear, in. Diametral pitch, teeth/in. Minor, or working depth diameter of gear, in. Number of teeth per gear Pitch diameter, in. The whole number in dividend when N9 is divided by number of planets The whole number in dividend when Nr is divided by number of planets Increment for locating planet gear Angular location of planet gear
Y o u have decided to design a planetary-gear system with a certain gear ratio, and have chosen the number of teeth for each gear to get that ratio. Will it work? Will the gears fit together to make a workable system? If they can pass the following five tests, they will.
2—Will the gears mate at the pitch diameters? This equation shows whether the planet gear will fill the space between the sun gear and the ring gear:
1—Do all gears have the same circular pitch? If they do not, the gears will not mesh.
Plonef gear
Ring gear
CP
PD
Sun gear
PD
Circular pitch CP = TT/DP = PD/N
Circular pitch and number of teeth determine pitch diameter, which leads to the next test:
3-WiII the teeth mesh? Gears that pass the first two tests will not necessarily pass this one. If the gears have the wrong number of
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teeth, the planet gear will not mesh with the sun gear and the ring gear at the same time. Gears with numbers of teeth divisible by three will mesh. There arc two other possible cases. Case I—The number of teeth on the sun gear divides evenly into the number of teeth on the ring gear. This set will mesh7 if allowance is made by spacing the planet gears unevenly around the sun gear.
134 = 0.3311. The answers agree to four places, so the gears will mesh. If the answers don't agree to four places, there will be interference. Angle a = 0.3311 x 360 = 119.2° 4—Can three planets fit around the sun gear?
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EXAMPLE: In a set of planetary gears the ring gear has 70 teeth, the sun gear 14 teeth and each of the three planet gears 28 teeth. Even spacing would place the planet gears every 120°, but in this case they must be placed slightly to one side of the 120° point to mesh. Since N, divides evenly into Nr there is a tooth on the ring gear opposite every tooth on the sun gear. Therefore, it is possible to fit a planet gear opposite any tooth on the sun gear. Tooth 6, five circular pitches from tooth I7 is the choice because it is closest to being one-third of the way around. It is opposite tooth 26 on the ring gear, because Ni/Ns = 70/14 = 25/5. Case II—The number of teeth on the sun gear does not divide evenly into the number of teeth on the ring gear. This set may or may not mesh; the following example shows how to tell.
They will if the major diameters adhere to the limitation Mp + mB/2 < m r by a safety clearance of & in. more than maximum tolerances.
5—Will irregularly spaced planets hit each other?
EXAMPLE: In a set of planetary gears with three planets, the ring gear has 134 teeth, the sun gear 14 and the planet gears 60 each. N 5 /3 = 14/3 = 4.67, so the whole number x = 4. N r / 3 = 134/3 = 44.67, so the whole number y = 44. Plug these numbers into the locating equation (x+z) Nr/Ns=y+{\-z) = {4.+z) 134/14 =44+(I-s) 10.57 z = 6.72 z = 0.636 Location of the planet gear as a fractional part of the circular distance around the set is (x + z)/N, = 4.636/14 = 0.3311, and y + (1 - z)/Nr = 44.364/
Two adjacent planets will not hit each other if 2L sin (180 — a) > Mp + A in. safety clearance. Sunto-planet center-to-center distance L — (PD, + PD,)/2.
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E p i c y c l i c
G e a r
T r a i n s
M. R Spotts
EPICYCUC GEAR TRAIN shown in Fig.
1 has Arm
A
While the foregoing was taking place gears D and E were rotating on each other through the equal arcs ed and e/. Gear E will have been turned in the reverse direction through angle BNJN0 X NJN9 The net effect of these two operations is to move the point of gear E, which was originally vertical at g, over to location /. Gear E has thus been rotated through angle
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integral with the right hand shaft. Gears C and D are keyed to a short length of shaft which is mounted in a bearing in Arm A, Gear C meshes with the fixed internal gear B. Gear D meshes with internal gear E which is keyed to the left hand shaft. To find the ratio of the speed of shaft E to the speed of shaft A proceed as follows. Let Nb be the number of teeth in gear B, Nc the number in gear C9 and so on. Let arm A, which was originally in a vertical position, be given an angular drsplacement 0. In so doing gear C will traverse through arc ab on gear B. Arc be of gear C must be equal to arc ab of gear B. Since angles are inversely proportional to radii, or to the number of teeth, gears C and D will have turned through angle BNJNC.
(1 - N^NJN0N,) B
This latter value when divided by 0, the angular movement of shaft A, gives the ratio of the rotations of shafts E and A respectively. This method of analysis gives a graphical representation of the movement of all the parts. It may be easily applied to all types of epicyclic systems including those containing bevel gears. Additional examples are shown in Figs. 2 to 6 inclusive. Either of shafts A or E may be used as the driver.
Fixed-
FiG. 1
Drive and driven shafts rotate in same direction
Fixed-
FIG. 2
Drive and driven shafts rotate in opposite directions
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Fixed FIG. 3
Drive and driven shafts rotate in same direction Equation is valid for Nc=Nd, and for Nc>Nd
Fixed-
FIG. 4
Drive and driven shafts rotate in same direction Equation is valid for Nc=Nd, and for Ne>Nd
Fixect-
FIG. 5
Drive and driven shafts rotate in opposi+e directions
Fixed-
FIG.6 Drive and driven shafts rotate in same direction
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C y c l o i d
G e a r
M e c h a n i s m s
Cycloidal motion is becoming popular for mechanisms in feeders and automatic machines. Here are arrangements, formulas, and layout methods.
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Preben W. Jensen
rpHE appeal of cycloidal mechanisms is that they can JL easily be tailored to provide one of these three common motion requirements: • Intermittent motion—with either short or long dwells • Rotary motion with progressive oscillation—where the output undergoes a cycloidal motion during which the forward motion is greater than the return motion • Rotary-to-linear motion with a dwell period All the cycloidal mechanisms covered in this article are geared; this results in compact positive devices capable of operating at relatively high speeds with little
H y p o c y c l o i d
backlash or "slop." The mechanisms can also be classified into three groups: Hypocycloid—where the points tracing the cycloidal curves are located on an external gear rolling inside an internal ring gear. This ring gear is usually stationary and fixed to the frame. Epicycloid—where the tracing points are on an external gear which rolls in another external (stationary) gear Pericycloid—where the tracing points are located on an internal gear which rolls on a stationary external gear.
M e c h a n i s m s
2» Double-dwell mechanism
1* Basic hypocycloid curves
lnpul cranky
Ring gear (fixed) Cusp curve Input crank
Driving pin
Planet gear
Plonet gear
Diamond-type Curve Loop curve
Reciprocaiing link (output)
Output curve
Coupling the output pin to a slotted member produces a prolonged dwell in each of the extreme positions. This is another application of the diamond-type hypocycloidal curve.
Input drives a planet in mesh with a stationary ring gear. Point P1 on the planet gear describes a diamond-shape curve, point P2 on the pitch line of the planet describes the familiar cusp curve, and point P.y, which is on an extension rod fixed to the planet gear, describes a loop-type curve. In one application, an end miller located at Px was employed in production for machining a diamond-shape profile.
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4. Internal-geneva drive
3 . Long-dwell geneva drive Locking cam
Driving pin
Geneva wheel
Input,
Geneva wheel (output)
Driving pin
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Input
Loop-type curve permits driving pin to enter slot in a direction that is radially outward from the center, and then loop over to rapidly index the cross member. As with the previous geneva, the output rotates 90 deg, then goes into a long dwell period during each 270deg rotation of the input.
As with standard four-station genevas, each rotation of the input indexes the slotted geneva 90 deg. By employing a pin fastened to the planet gear to obtain a rectangular-shape cycloidal curve, a smoother indexing motion is obtained because the driving pin moves on a noncircular path. 5. Cycloidal parallelogram
Input cranks
Transcribed curve
Double cycloids
Two identical hypocycloid mechanisms guide the point of the bar along the triangularly shaped path. They are useful also in cases where there is limited space in the area where the curve must be described. Such doublecycloid mechanisms can be designed to produce other types of curves.
7. Cycloidal rocker
input crank
6. Short-dwell rotary
Driving pin Input .crank
Rocker displacement.deg
Output-
Approximately an arc of a circle
Rocker (output)
Dwell period
Input rotation.deg
Here the pitch circle of the planet gear is exactly one-quarter that of the ring gear. A pin on the planet will cause the slotted output member to have four instantaneous dwells for each revolution of the input shaft.
The curvature of the cusp is approximately that of an arc of a circle. Hence the rocker comes to a long dwell at the right extreme position while point P moves to P'. There is then a quick return from P' to F\ with a momentary dwell at the end of this phase. The rocker then undergoes a slight oscillation from point P" to P'", as shown in the displacement diagram.
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8. Cycloidal reciprocator
9. Adjustable harmonic drive Dwell with very slight oscillation
Output
Reciprocating output
curve
Stroke
Connecting rod
Adjusting lever input crank Straight output
instantaneous dwell
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Driving pin
Input
Driving pin
Input, 360 deg
By making the planet-gear half that of the internal gear, a straight-line output curve is produced by the driving pin which is fastened to the planet gear. The pin engages the slotted member to cause the output to reciprocate back and forth with harmonic (sinusoidal) motion. The position of the fixed ring gear can be changed by adjusting the lever, which in turn rotates the straight-line output-curve. When the curve is horizontal, the stroke is at a maximum; when the curve is vertical, the stroke is zero.
Points of instantaneous dwell
Portion of curve, P-P\ produces the long dwell (as in previous mechanism), but the five-lobe cycloidal curve avoids a marked oscillation at the end of the stroke. There are also two points of instantaneous dwell where the curve is perpendicular to the connecting rod.
10« Elliptical-motion drive Shaft to be machined
Ptanetgear
Output curves,
By making the pitch diameter of the planet equal to half that of the ring gear, every point on the planet gear (such as points P2 and Ps) will describe elliptical curves which get flatter as the points are selected closer to the pitch circle. Point P2, at the center of the planet, describes a circle; point P^ at the pitch circle describes a straight line. When a cutting tool is placed at P3, it will cut almost-flat sections from round stock, as when machining a bolt. The other two sides of the bolt can be cut by rotating the bolt, or the cutting device, 90 deg. (Reference: H. Zeile, Unrund- und Mehrkantdrehen, VDI-Berichte, Nr. 77,1965.)
E p i c y c l o i d
Positions of driving pin
Machinedflat
M e c h a n i s m s
11. Epicycloid reciprocator
Driving link Driving pin
Output slider
Guides Input crank
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Here the sun gear is fixed and the planet gear driven around it by means of the input link. There is no internal ring gear as with the hypocycloid mechanisms. Driving pin P on the planet describes the curve shown which contains two almost-flat portions. By having the pin ride in the slotted yoke, a short dwell is produced at both the extreme positions of the output member. The horizontal slots in the yoke ride the endguides, as shown.
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12. Progressive oscillating drive
Output link
Output curves
13« Parallel-guidance mechanisms
Output Hnk
Driving /ink (fixed to planet)
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input crank
input crank
By fixing a crank to the planet gear, a point P can be made to describe the double loop curve illustrated. The slotted output crank oscillates briefly at the vertical portions.
M o t i o n
The input crank contains two planet gears. The center sun-gear is fixed as in the previous epicycloid mechanisms. By making the three gears equal in diameter and having gear 2 serve as an idler, any member fixed to gear 3 will remain parallel to its previous positions throughout the rotation of the input ring crank.
E q u a t i o n s
14, Equations for epicycloid drives
The equations for angular displacement, velocity and acceleration for basic epicyclic drive are given below. (Reference: Schmidt, E. H., "Cycloidal Cranks," Transactions of the 5th Conference on Mechanisms, 1958, pp 164-180):
P/onetgeor
Sun gear input
Output
Driving pin
Symbols.
Starting position both input 8 output in this position
Angular displacement
(D
Angular velocity
(2)
Angular acceleration
(3)
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angular acceleration of output, deg/sec2 radius of driving pin from center of planet gear pitch radius of planet gear pitch radius of fixed sun gear angular velocity of output, deg/sec angular displacement of output, deg BR/r input displacement, deg angular velocity of input, deg/sec
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15* Equations for hypocycloid drives (4)
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(5)
D e s c r i b i n g
A p p r o x i m a t e
S t r a i g h t
(6)
L i n e s
16. Gear rolling on a gear—flatten curves It is frequently desirable to find points on the planet gear that will describe approximately straight lines for portions of the output curve. Such points will yield dwell mechanisms, as shown in Fig 2 and 11. Construction is as follows (shown at left): 1. Draw an arbitrary line PB. Planet gear 2. Draw its parallel O>A. 3. Draw its perpendicular PA at P. Locate point A. 4. Draw O1A. Locate W1. 5. Draw perpendicular to PW1 at W1 to locate W. 6. Draw a circle with PW as the diameter. All points on this circle describe curves with portions that are approximately straight. This circle is also called the inflection circle because all points describe curves which have a point of inflection at the position illustrated. (Shown is the curve passing through point W.) Sun gear
17, Gear rolling on a rack—vee curves
Inflection circle
18. Gear rolling inside a gear—zig-zag
Roiling gear
Ring gear (stationary)
Planet gear
Inflection cirde
Gear rock.
This is a special case. Draw a circle with a diameter half that of the gear (diameter O1P). This is the inflection circle. Any point, such as point W1, will describe a curve that is almost straight in the vicinity selected. Tangents to the curves will always pass through the center of the gear, O1 (as shown).
To find the inflection circle for a gear rolling inside a gear: 1. Draw arbitrary line PB from the contact point P. 2. Draw its parallel O1A, and its perpendicular, PA. Locate A. 3. Draw line AOx through the center of the rolling gear. Locate W\, 4. Draw a perpendicular through W1. Obtain W. Line WP is the diameter of the inflection circle. Point Wu which is an arbitrary point on the circle, will trace a curve of repeated almost-straight lines, as shown.
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19. Center of curvature—gear rolling on gear
20- Center of curvature—gear rolling on a rack
Coupler point
Revolving planet gear Center of curvature, CQ,
Roiling gear
Stationary sun gear
Co py rig hte dM ate ria l
Gear racfc
Construction is similar to that of the previous case. 1. Draw an extension of line CP. 2. Draw a perpendicular at P to locate A. 3. Draw a perpendicular from A to the straight suface to locate C0.
2 1 . Center of curvature—gear rolling inside a gear
By locating the centers of curvature at various points, one can then determine the proper length of the rocking or reciprocating arm to provide long dwells (as required for the mechanisms in Fig 7 and 8), or proper entry conditions (as for the drive pin in the mechanism in Fig 3). In the case of a gear with an extended point, point C, rolling on another gear, the graphical method for locating the center of curvature is given by these steps: 1. Draw a line through points C and P. 2. Draw a line through points C and O1. 3. Draw a perpendicular to CP at P. This locates point A. 4. Draw line AO'.?, to locate C1, the center of curvature.
22. Analytical solutions
Coupler point
Revolving planet gear
Inferno! ring gear
1. Draw extensions of CP and CO1. 2. Draw a perpendicular of PC at P to locate A. 3. Draw AO2 to locate C0.
The centure of curvature of a gear rolling on a external gear can be computed directly from the EulerSavary equation:
= constant (7)
Revolving planet gear
Stationary sun gear
where angle $ and r locate the position of C. By applying this equation twice, specifically to point O1 and O^ which have their own centers of rotation, the following equation is obtained:
or
This is the final design equation. All factors except rr are known; hence solving for r, leads to the location of C. For a gear rolling inside an internal gear, the Euler-Savary equation is
constant which leads to
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2 3 . Hypocycloid substitute Driving pin
Driving pin Oufput gear
Oufpuf gear
Input link
Coupler
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input link
It is not always realized that cycloid mechanisms can frequently be replaced by other cycloids that produce the same motion and yet are more compact. The mechanism (right) is a typical hypocycloid. Gear 1 rolls inside gear 2 while point C describes a hypocycloid curve. To find the substitute mechanism, draw parallels OsO2 and OsC to locate point P2. Then select O2P2 as the new radius of the large (internal) gear. Line P2O3 becomes the radius of the small gear. Point C has the same relative position and can be obtained by completing the triangles. The new mechanism is about two-thirds the size of the original.
Originol mechanism
Substitute
2 4 . Epicycloid substitute
Oufput
Ring gear (output)
Input link
Fixed sun gear
Output
The equivalent mechanisms of epicycloids are pericycloids in which the planetary gear is stationary and the output is taken from the ring gear. Such arrangements usually lead to a more-compact design. In the above mechanism, point C traces an epicycloidal curve. Draw the proper parallels to find P2, then use P2Os to construct the compact substitute mechanism shown at right of original.
Input
Original mechanism
2 5 . Multigear substitute
input link
Output tint
Original ring gear
Original planet gear
Substitute
This is another way of producing a compact substitute for a hypocycloid mechanism. The original mechanism is shown in dashed lines—gear / rolls inside gear 2 and point C describes the curve. The three external gears (gears 3, 4y and 5) replace gears 1 and 2 with a remarkable savings in space. The only criterion is that gear 5 must be one-half the size of gear 3: gear 4 is only an idler. The new mechanism thus has been reduced to approximately one-half that of the original in size.
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C a r d a n - G e a r
M e c h a n i s m s
These gearing arrangements convert rotation into straight-line motion, without need for slideways.
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Sigmund Rappaport
Cardan gearing . . . works on the principle that any point on the periphery of a circle rolling on the inside of another circle describes, in general, a hypocyloid. This curve degenerates into a true straight line (diameter of the larger circle) if diameters of both circles are in the ratio of 1:2. Rotation of input shaft causes small gear to roll around the inside of the fixed gear. A pin located on pitch circle of the small gear describes a straight line. Its linear displacement is proportional to the theoretically true sine or cosine of the angle through which the input shaft is rotated. Among other applications, Cardan gearing is used in computers, as a component solver (angle resolver).
Adjustment mark
Adjustment angle
Outer gear-
Cardan gearing and Scotch yoke * . . in combination provide an adjustable stroke. Angular position of outer gear is adjustable. Adjusted stroke equals the projection of the large dia, along which the drive pin travels, upon the Scotch-yoke centerline. Yoke motion is simple harmonic.
Adjustment clamps
Adjusted stroke Max. stroke
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Valve drive . . . exemplifies how Cardan principle may be applied. A segment of the smaller circle rocks to and fro on a circular segment whose radius is twice as large. Input and output rods are each attached to points on the small circle. Both these points describe straight lines. Guide of the valve rod prevents the rocking member from slipping.
Fixed gear-
Radius, r
Radius, 2r<
Input shaft
Tatal shake=40
Simplified Cardan principle , , . does away with need for the relatively expensive internal gear. Here, only spur gears may be used and the basic requirements should be met, i.e. the 1;2 ratio and the proper direction of rotation. Latter requirement is easily achieved by introducing an idler gear, whose size is immaterial. In addition to cheapness, this drive delivers a far larger stroke for the comparative size of its gears.
Position 2
Rearrangement of gearing . . . in (4) results in another useful motion. If the fixed sun-gear and planet pinion are in the ratio of 1:1, then an arm fixed to the planet shaft will stay parallel to itself during rotation, while any point on it describes a circle of radius R. An example of application: in conjugate pairs for punching holes on moving webs of paper.
Planet pinion
Arm remains parallel
Planet shaft
Fixed sun gear
Arm Posit/an /
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T y p i c a l f o r
M e t h o d s
G e a r
o f
P r o v i d i n g
L u b r i c a t i o n
S y s t e m s
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Below are shown various lubricating systems that can serve as guides when designing for successful, efficient gear systems.
DRIP OILING
BRUSH APPLICATION
CAN APPLICATION
Holes in feed line
Pump,
Reservoir
WORM GEAR SET
FORCE-FEEO LUBRICATION
Low-speed herringbone i gears
Oil baih
OPEN GEAR
Pressure Storage
Fitter un/fs Clean-of/ chamber Settling chamber •
'Oi/ reservoir
Heavy oil in reservoir
Strainers
CENTRAL OILING SYSTEM
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OPEN WORM GEARS
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Gravity oil feed to bearings
low-speech rotary kiln
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Oil cups for bearings
Lubrication appliedby swab to gears
Sed/'meht chamber
SPLASH SYSTEM
Cast pockets catch oil splash which then runs over bearings
OPEN BEVEL AND SPUR REDUCTION GEARS
Filling and inspection plate
Measuring -^ rod\
Low-speed shaft
Baffles
Check valves
Pump
/Reservoir
SPLASH-LUBRICATED GEARS
Reservoir
Pump
Oil reservoir
DIRECT SPLASH LUBRICATION
LUBRICATION FOR BOTH DIRECTIONS A// sketches courtesy Socony- Vacuum Oi/ Company, /nc.
Reservoir
UNOER-ORIVEN WORM SET
Pressure gage Pump Reservoir
Sue ft on
SELF-CONTAINED UUBRICATtON SYSTEM
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OVER-DRIVEN WORM SET
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
7
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CLUTCHES Basc i Types of Mechanc ial Cu ltches Construco tin Detas li of Overd in ig Cu ltches 10 Ways to Appyl Overunnn ig Cu ltches LowC -ost Desg ins for Overunnn ig Cu ltches Smal Mechanc ial Cu ltches for Precs ie Servc ie Centrfiugal Cu ltches Serated Cu ltches and Detents Sprn ig Bands Grp i Tg ihty l to Drv ie Overunnn ig Cu ltch Accurate Sou lto in for Ds ik-Cu ltch Torque Capacty i Sprn ig-Loaded Pn is Ad i Sprags in OneW - ay Cu ltch Roe lr-Type Cu ltch
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7-2 7-4 7-6 7-8 7-10 7-12 7-16 7-18 7-19 7-20 7-20
B a s i c
T y p e s
o f
M e c h a n i c a l
C l u t c h e s
Sketches include both friction and positive types. Figs. 1-7 are classified as externally controlled; Figs. 8-12 are internally controlled. The latter are further divided into overload relief, over-riding, and centrifugal types. Marvin Taylor
Cam
Planet carrier
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Dr/'v/ng shaft
Ring gear
Top View
Cam
Key
Driving member-
Driven shaft
Sun gear
Control arm
Fig.l
Driven shaft-
SLIDING KEY CLUTCH. Driven shaft with a keyway carries freely-rotating member which has radial slots along its hub; sliding key is spring loaded but is normally restrained from engaging slots by the control cam. To engage the clutch, control cam is raised and key
2•
Drum-
Fig.7
Shoe
Control arm
Q PLANETARY TRANSMISSION CLUTCH. In disen&• gaged position shown, driving sun gear will merely cause the free-wheeling ring gear to idle counter-clockwise, while the driven member, the planet carrier, remains motionless. If motion of the ring gear is blocked by the control arm, a positive clockwise drive is established to the dri\cn planet carrier.
Driven shaft
Fig,8
SPRING AND BALL RADIAL DETENT CLUTCH. This design will positively hold the driving gear and driven shaft in a given timing relationship until the torque becomes excessive. At this point the balls will be forced inward against their spring pressure and out of engagement with the holes in the hub, thus permitting the driving gear to continue rotating while the driven shaft is stationary.
8•
enters one of the slots. To disengage, cam is lowered into the path of the key; rotation of driven shaft forces key out of slot in driving member. Step on control cam limits axial movement of the key.
Driving gear
EXPANDING SHOE CLUTCH. In sketch above, engagement is obtained by motion of control arm which operates linkages to force friction shoes radially outward into contact with inside surface of drum.
7•
Fig.3
Fig.2
JAW CLUTCH. Left sliding half is feathered to the driving shaft while right half rotates freely. Control arm activates the sliding half to engage or disengage the drive. This clutch, though strong and simple, suffers from disadvantages of high shock during engagement, high inertia of the sliding half, and considerable axial motion required for engagement.
I•
Control
Fig.9
CAM AND ROLLER CLUTCH. This over-running clutch is suited for higher speed free-wheeling than the pawl and ratchet types. The inner driving member has camming surfaces at its outer riin and carries light springs that force rollers to wedge between these surfaces and the inner cylindrical face of the driven member. During driving, self-energizing friction rather than the springs forces the roller to tightly wedge between the members and give essentially positive drive in a clockwise direction. The springs insure fast clutching action. If the driven member should attempt to run ahead of the driver, friction will force the rollers out of a tight wedging position and break the connection.
9•
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ControlFig. 5
Fig.6
Driven gear
Fig.4
Driving
Control arm
Con fro I arm
ratchet
M PAWL AND RATCHET CLUTCH. (External Con^* trol). Ratchet is keyed to the driving shaft; pawl is carried by driven gear which rotates freely on the driving shaft. Raising the control member permits the spring to pull the pawl into engagement with the ratchet and drive the gear. Engagement continues until control member is lowered into the path of a camming surface on the pawl. The motion of the driven gear will then force the pawl out of engagement and bring the driven assembly to a solid stop against the control member. This clutch can be converted into an internally controlled type of unit by removing the external control arm and replacing it with a slideable member on the driving shaft.
C PLATE CLUTCH. Available in many variations, **• with single and multiple plates, this unit transmits power through friction force developed between the faces of the left sliding half which is fitted with a feather key and the right half which is free to rotate on the shaft. Torque capacity depends upon the axial force exerted by the control member when it activates the sliding half.
# CONE CLUTCH. This type also requires axial **• movement for engagement, but the axial force required is less than that required with plate clutches. Friction material is usually applied to only one of the mating surfaces. Free member is mounted to resist axial thrust. Driving shaft
Driven member
Gland
Fig. 10
Fig.ll
IQ WRAPPED SPRING CLUTCH. Makes a simple '"• and inexpensive uni-directional clutch consisting of two rotating members connected by a coil spring which fits snugly over both hubs. In the driving direction the spring tightens about the hubs producing a self energizing friction grip; in the opposite direction it unwinds and will slip. ii EXPANDING SHOE CENTRIFUGAL CLUTCH. ''• Similar in action to the unit shown in Fig. 7 with the exception that no external control is used. Two friction shoes, attached to the driving member, are held inward by springs until they reach the "clutch-in" speed, at
Driven member Driving shaft
Plates Fig.12
which centrifugal force energizes the shoes outward into contact with the drum. As the driver rotates faster the pressure between the shoes and the drum increases thereby providing greater torque capacity.
IQ MERCURY GLAND CLUTCH. Contains two fric•*• tion plates and a mercury filled rubber gland, all keyed to the driving shaft. At rest, mercury fills a ring shaped cavity near the shaft; when revolved at sufficient speed, the mercury is forced outward by centrifugal force spreading the rubber gland axially and forcing the friction plates into driving contact with the faces of the driven housing. Axial thrust on driven member is negligible.
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C o n s t r u c t i o n
D e t a i l s
o f
O v e r r i d i n g
C l u t c h e s A. DeFeo Oscillating motion of driving shaft
Gravitational force engages driving pawl
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Resultant intermittent motion
Intermittent motion of driven wheel
(B)
Elementary over-riding clutches: (A) Ratchet and Pawl mechanism is used to convert reciprocating or oscillating movement to intermittent rotary motion. This motion is positive but limited to a multiple of the tooth pitch. (B) Friction-
(C)
type is quieter but requires a spring device to keep eccentric pawl in constant engagement. (C) Balls or rollers replace the pawls in this device. Motion of the outer race wedges rollers* against the inclined surfaces of the ratchet wheel.
Over-running motion of outer race moves sprags out of locked position
Springs on each sJde hold sprags in contact with races
Direction of drivina
Morse-Form Sprag
4
Intermittent motion of driven ratchet wheel
Friction locking pawl
Locking pawl
(A)
1
Oscillating motion of outer ring
Counter -clockwise motion wedges curved pawl tightly against driven wheel
(B)
Sprags in over-running position
(A)
With cylindrical inner and outer races, sprags are used to transmit torque. Energizing springs serves as a cage to hold the sprags. (A) Compared to rollers, shape of sprag permits a greater number within a limited space; thus higher torque loads
Power is transmitted through splined clutch plates
Wedging angle
Sprags under torque load
are possible. Not requiring special cam surfaces, this type can be installed inside gear or wheel hubs. (B) Rolling action wedges sprags tightly between driving and driven members. Relatively large wedging angle insures positive engagement.
Springs maintain plate clearance and bati$ in starting position
Threaded case adjustment
View A
Driving motion
Thrust bearing
Pilot bearing for overrun action
Kinnty M'f'g Co.
Driven or over running shaft
6
Driving shaft
Spiined member actuates ball and cam device
Multi-disk clutch is driven by means of several sinteredbronze friction surfaces. Pressure is exerted by a cam actuating device which forces a series of balls against a disk plate. Since a small part of the transmitted torque is carried by
Bail exerts working pressure on clutch plates View A
the actuating member, capacity is not limited by the localized deformation of the contacting balls. Slip of the friction surfaces determine the capacity and prevent rapid, shock loads. Slight pressure of disk springs insure uniform engagement.
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Direction of driven or over-riding member
Outer race Roller cage.
Side lug
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Extended sleeve for attaching gear sprocket or sheave
Cam surface
Driving shaft
Centrifugal weight
The Milliard Corp.
2
Commercial over-riding clutch has springs which hold rollers in continuous contact between cam surfaces and outer race; thus there is no backlash or lost motion. This simple design is positive and quiet. For operation in the opposite direction, the roller mechanism can easily be reversed in the housing.
Heavy coil spring
Small clearance
A
No clearance
Centrifugal force can be used to hold 3race.rollers in contact with cam and outer Force is exerted on lugs of the cage which controls the position of the rollers.
First coif exerts slight pressure on inside surface
Small spring m is the "trigger
Lubrication grooves
LGS. Spring Clutch Corp.
5
Engaging device consists of a helical spring which is made up of two sections: a light trigger spring and a heavy coil spring. It is attached to and driven by the inner shaft. Relative motion of outer member rubbing on trigger causes this spring to
Section A-A
wind-up. This action expands the spring diameter which takes up the small clearance and exerts pressure against the inside surface until the entire spring is tightly engaged. Helix angle of spring can be changed to reverse the over-riding direction.
Position of slightly worn roller
Cage motion moves rollers into engagement on cam surface
Straight cam surface
Cam
Increased wedging angle
Initial position of roller
Curved cam surface (B) Wedging angle remains constant
(A)
7
Free-wheeling clutch widely used in power transmission has a series of straight-sided cam surfaces. An engaging angle of about 3 deg is used; smaller angles tend to become locked and are difficult to disengage while larger ones are not as
effective. (A) Inertia of floating cage wedges rollers between cam and outer race. (B) Continual operation causes wear of surfaces; 0.001 in. wear alters angle to 8.5 deg. on straightsided cams. Curved cam surfaces maintain constant angle.
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1 0
W a y s
t o
A p p l y
O v e r r u n n i n g
C l u t c h e s
These clutches allow freewheeling, indexing, and backstopping applicable to many design problems. Here are some clutch setups. W. Edgar Mulholland & John L. King, Jr. Gear 2 Output
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Clutch 2 (freewheeling) Overrunning motion of outer race moves sprags out of locked position
Power path
Motor pinion Input
jSprogs in overrunning Wedging angle position Sprags under torque load Clutch I (driving) Gear I Precision Sprags . . . act as wedges and are made of hardened alloy steel. In the Formsprag clutch, torque is transmitted from one race to another by wedging action of sprags between the races in one direction; 2-Speed Drive —I . . . in other direction the clutch freewheels. requires input rotation to be reversible. Counterclockwise input as shown in the diagram drives gear 7 through clutch 7; output is counterclockwise; clutch 2 over-runs. Clockwise input (schematic) drives gear 2 through clutch 2; output is still counterclockwise; clutch 7 over-runs. l$hptl?50rpm motor
Driven wheel
2hpt $70rpm motor
2-Speed Drive —Il . . . for grinding wheel can be simple, in-line design if over-running clutch couples two motors. Outer race of clutch is driven by gearmotor; inner race is keyed to grinding-wheel shaft. When gearmotor drives, clutch is engaged; when larger motor drives, inner race over-runs.
Clutch-coupling
Locating pin Indexing table Rack
Overrunning dutch
Driving Driven motor fan Housing Fan Freewheels . . . when driving power is shut off. Without overrunning clutch, fan momentum can cause belt breakage. If driving source is a gearmotor, excessive gear stress may also occur by feedback of kinetic energy from fan.
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Locating holes Gear
Clutch permits feed only on forward stroke
Indexing Table . . . is keyed to clutch shaft. Table is rotated by forward stroke of rack, power being transmitted through clutch by its outer-ring gear only during this forward stroke. Indexing is slightly short of position required. Exact position is then located by spring-loaded pin, which draws table forward to final positioning. Pin now holds table until next power stroke of hydraulic cylinder
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Flywheel-
' Clutch prevents reverse rotation
Adjustable crank throw
Frame
Punch Die Clutch with gear on outer race
Hopper
-Reciprocating rack Feed roll Stock
Punch Press Feed .. is so arranged that strip is stationary on downstroke of punch (clutch freewheels); feed occurs during upstroke when clutch transmits torque. Feed mechanism can easily be adjusted to vary feed amount.
Gear
Clutch drives roll to one direction only RoIL
Reciprocot" ing action
Pinion keyed to outer ring of clutch
Indexing and Backstopping . . . is done with two clutches so arranged that one drives while the other freewheels. Application here is for capsuling machine; gelatin is fed by the roll and stopped intermittently so blade can precisely shear material to form capsules.
Feed /of/ moves in some direct/on
Inner (ace moves reciprocating// Adjustable eccentric
C/utch and gear on feed* roil L/nkage Pivot point Path of eccentric
Output shaft
Drive (inks
dutches (one overrides while other drives)
Intermittent Motion . . . of candy machine is adjustable; function of clutch is to ratchet the feed rolls around. This keeps the material in the hopper agitated.
Control link
Zero
Control-link movement
Drive link
Pinion with double eccentric Eccentric strap Input shaft
Double-impulse Drive . . . employs double eccentrics and drive clutches. Each clutch is indexed 180° out of phase with the other. One revolution of eccentric produces two drive strokes. Stroke length, and thus the output rotation, can be adjusted from zero to max by the control link.
Overrunning clutches (A)
(B)
Anti-backlash Device . . . uses over-running clutches to insure that no backlash is left in the unit. Gear A drives B and shaft Il with the gear mesh and backlash as shown in (A). The over-running clutch in gear C permits gear D (driven by shaft II) to drive gear C and results in the mesh and backlash shown in (B). The over-running clutches never actually over-run. They provide flexible connections (something like split and sprung gears) between shaft 1 and gears A, C to allow absorption of all backlash.
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L o w - C o s t
D e s i g n s
f o r
O v e r r u n n i n g
C l u t c h e s
All are simple devices that can be constructed inexpensively in the laboratory workshop. James F. Machen
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Slides in shaft
A
Lawnmower type
Housing con be stock of stompings
B
Wedging balls or rollers: internal CA); external (B)
Nylon or similor moterio!
Molded sprags (for light duty)
Spring-retaining collars
Drive
Disengaging idler rises in slot when drive direction is reversed
Grips when driven\ slips for overrun
Spline
Spring loaded Slip-spring coupling
Internal ratchet and spring-loaded pawls
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One-way dog clutch
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(FOR ANGULAR AND AXIAL ADJUSTMENT) Optional groove or depression in female member
Tapered threaded plug
-Tapered end
Socket screw
Socket screw 1,2 or 3 bolls may be used
Plug jam (with four axial slots)
Ball jam
Sliding wedges
No slide
Clomp bolt
Clamped wedges (for axial adjustment only)
Slide
Push-button release
One-way slide-lock
Belleville washers Belleville-washer clamp
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Clomp nut
S m a l l f o r
M e c h a n i c a l
P r e c i s e
C l u t c h e s
S e r v i c e
Clutches used in calculating machines must have: (1) Quick response-lightweight moving parts; (2) Flexibility-permit multiple members to control operation; (3) Compactness-for equivalent capacity positive clutches are smaller than friction; (4) Dependability; and (5) Durability.
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Marvin Taylor
PAWL AND RATCHET SINGLE CYCLE CLUTCH (Fig. 1 ) . Known as Dennis Clutch, parts B, C and D, are primary components, B, being the driving ratchet, C9 the driven cam plate and, D, the connecting pawl carryied by the cam plate. Normally the pawl is held disengaged by the lower portion of clutch arm A. "When activated, arm A rocks counter-clockwise until it is out of the path of rim F on cam plate C and permits pawl D under the effect of spring E to engage with ratchet B. Cam plate C then turns clockwise until, near the end of one cycle, pin G on the plate strikes the upper part of arm A camming it clockwise back to its normal position. The lower part of A then performs two functions: (1) cams pawl D out of engagement with the driving ratchet B and (2) blocks further motion of rim F and the cam plate.
Fig.!
PAWL AND RATCHET SINGLE CYCLE DUAL CONTROL CLUTCH—(Fig. 2 ) . Principal parts are: driving ratchet, B9 directly connected to the motor and rotating freely on rod A; driven crank, C9 directly connected to the main shaft of the machine and also free on A; and spring loaded ratchet pawl, D9 which is carried by crank, C, and is normally held disengaged by latch £. To activate the clutch, arm F is raised, permitting latch E to trip and pawl D to engage with ratchet B. The left arm of clutch latch G, which is in the path of the lug on pawl D, is normally permitted to move out of interference by the rotation of the camming edge of crank C. For certain operations block / / is temporarily lowered, preventing motion of latch G, resulting in disengagement of the clutch after part of the cycle until subsequent raising of block H permits motion of latch C and resumption of the cycle.
Fig.2
PLANETARY TRANSMISSION CLUTCH (Fig. 3 ) . A positive clutch with external control, two gear trains to provide bi-directional drive to a calculator for cycling the machine and shifting the carriage. Gear A is the driver, gear L the driven member is directly connected to planet carrier F. The planet consists of integral gears B and C; B meshing with sun gear A and free-wheeling ring gear G, and C meshing with free-wheeling gear £>. Gears D and G carry projecting lugs, E and H respectively, which can contact formings on arms / and K of the control yoke. When the machine is at rest, the yoke is centrally positioned so that the arms J and K are out of the path of the projecting lugs permitting both D and G to free-wheel. To engage the drive, the yoke rocks clockwise as shown, until the forming on arm K engages lug H blocking further motion of ring gear G. A solid gear train is thereby established driving F and L in the same direction as the drive A and at the same time altering the speed of D as it continues counter-clockwise. A reversing signal rotates the yoke counter-clockwise until arm J encounters lug E blocking further motion of D. This actuates the other gear train of the same ratio.
Fig. 3 (a)
(b)
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Cycle
Fig.4
MULTIPLE DISK FRICTION CLUTCH (Fig. 4 ) . Two multiple disk friction clutches are combined in a single two-position unit which is shown shifted to the left. A stepped cylindrical housing C enclosing both clutches is carried by self-lubricated bearing E on shaft J and is driven by the transmission gear H meshing with the housing gear teeth K. At either end, the housing carries multiple metal disks Q that engage key ways V and can make frictional contact with formica disks N which, in turn, can contact a set of metal disks P which have slotted openings for coupling with flats on sleeves B and W. In the position shown, pressure is exerted through rollers L forcing the housing to the left making the left clutch compact against adjusting nuts Rf thereby driving gear A via sleeve B which is connected to jack shaft J by pin V. When the carriage is to be shifted, rollers L force the housing to the right, first relieving the pressure between the adjoining disks on the left clutch then passing through a neutral position in which both clutches are disengaged and finally making the right clutch compact against thrust bearing F, thereby driving gear G through sleeve W which rotates freely on the jack shaft.
clutch
Shift
clutch
SINGLE PLATE FRICTION CLUTCH (Fig. 5 ) . The basic clutch elements, formica disk A, steel plate B and drum C, are normally kept separated by spring washer G. To engage the drive, the left end of a control arm is raised, causing ears F, which sit in slots in plates JF/, to rock clockwise spreading the plates axially along sleeve P. Sleeves E and P and plate B are keyed to the drive shaft; all other members can rotate freely. The axial motion loads the assembly to the right through the thrust ball bearings K against plate L and adjusting nut Mf and to the left through friction surfaces on A9 B and C to thrust washer S, sleeve E and against a shoulder on shaft D, thus enabling plate A to drive the drum C
Fig. 5
OVERLOAD RELIEF CLUTCH (Fig. 6 ) . This is a simply constructed, doubleplate, spring loaded, friction coupling. Shaft G drives collar £ which drives slotted plates C and D and formica disks B. Spring H is forced by the adjusting nuts, which are screwed on to collar E, to maintain the unit under axial pressure against the shoulder at the left end of the collar. This enables the formica disks B to drive through friction against both faces of the gear which is free to turn on the collar, causing output pinion J to rotate. If the machine should jam and pinion / prevented from turning, the motor can continue running without overloading
Copyright © 2005 by The McGraw-Hill Companies
Fig. 6
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C e n t r i f u g a l
C l u t c h e s
These simple devices provide low-cost clutching for machines operating under fast-changing load conditions.
I
Co py rig hte dM ate ria l
M. R Spotts
F you want a practical way of connecting a motor— or any other type of prime mover—to a load when frequent stopping and starting are involved, centrifugal clutches are a good bet. Low in initial cost, centrifugal clutches can save you the expense of buying another form of electric motor, not to mention auxiliary starting equipment. Centrifugal clutches are built in a wide range of sizes and types—all the way from the little gasoline cars run on tracks at funfairs (here the motor disengages at low speed, and as the child presses on the gas pedal the car starts moving) to 50O-hp diesei engines. Other advantages: These clutches are good starters for high-inertia loads. They tolerate a considerable amount of manufacturing variations and are well suited to drives that undergo vibrations and heavy shock loads. Delayed engagements are possible by varying the clutchspring force, and installation and service costs are low. A typical centrifugal clutch has a set of shoes that are forced out against the output drum by centrifugal force. The shoes may be loosely held within the drum (Fig 1, next page), but in the more refined designs the shoes are connected to the input member by means of a floating link (Fig 2) or a fixed pivot (Fig 5). Both attached-shoe designs (Fig 2 and 5) arc analyzed here. Until now, however, the design procedure has been basically a graphical one. The design formulas derived here obviate the need for a graphical layout (or the graphical solution can serve as a check).
area br dty of an element of lining, gives the normal force between lining and drum. The component of force parallel to the v-axis is found by multiplying by cos I/F. Eq 3L is substituted for p and the result integrated over the length of the lining, —/2 to <£/2, to obtain Nv> the component of normal force parallel to v-axis:
(2)
In a similar manner, the total component of normal force Nw parallel to the w-axis is found by multiplying by sin \jj. The integration gives
(3)
The accompanying friction forces are
(4) (5)
where p, is the coefficient of friction. The torque exerted by the shoe is found by multiplying the normal force on the element by /A, and multiplying again by r to give: Torque equation
Floating-link design
The shoe of this type (Fig 2) is supported at the free end H of the floating link BH. End R of the link is attached to the hub of the driving member. The lining contacts the drum of the driven member and covers an angle r/>, with support H at the midpoint which determines the v and w axes for the shoe. Angle 4> is large so pressure p between the lining and drum is not constant but varies according to the equation (D where plt is the maximum value of the lining pressure located at angle B to the v-axis. Angle ^ is the angle from the v-axis to the clement under consideration. The pressure on the lining p, when multiplied by the
(6)
(Eq 2 to 6 were obtained by G. A. G. Fazekas, "Graphical Shoe-Brake Analysis/' Trans. ASME, vol 79, 1957, p 1322.) The clutch shoe is in equilibrium from the following three forces: 1. An outward radial force consisting of the difference between the centrifugal force Fc on the shoe and the inward force Fx from the springs. 2. Force Q which is the resultant of the previously determined forces /V,., Nn., F1 and F11.. 3. Reaction R which must have a BH direction since this is a two-force member.
Copyright © 2005 by The McGraw-Hill Companies
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by the spring force Fs. The outward force Fc on the shoe is equal to: Centrifugal force
(10) where W is the weight of the shoe assumed to be concentrated at radius r«; w is the angular velocity, rad/sec, and g is the gravitational constant, 386 in./sec2. As shown in Fig 2, link BH is inclined at angle a to the v-axis. The sine theorem gives equations for:
Co py rig hte dM ate ria l
When a body with three forces is in equilibrium, the three forces must intersect at a single point. Because R and F{,—F11 intersect at //, force Q must pass through this point also. Fig 3 shows Q passing through H as the resultant of the other two forces. Since Q is also the resultant of the forces arising from p and /x /?, the moment made by such forces about H must be zero. This fact is utilized for finding 0, the inclination of the line of maximum pressure. The moment arms about H for p and ^p are marked in the figure. Then The value of the variable p from Eq 1 is substituted, and the resulting expressions are integrated between the limits of — <£/2 and <£/2. The result can be solved for tan 6 to give:
Forces R and F,-F,
(H)
Line of maximum pressure
Drum
(7)
When 6 is determined, the forces represented by Eq 2 to 5 inclusive can be found and added vectorially as shown in Fig 3. This gives:
Output pulley
Shoes.
Cage
Resultant of forces, Q
(8)
Input shoft
Inclination /3 of force Q
Lining
(9)
At low or idling speeds, the shoe is pulled inwardly
1. Free-shoe centrifugal clutch
SYMBOLS
width of lining centrifugal force spring force component along v-axis of friction lining force component along w-axis of friction lining force gravitational constant, 386 in./sec2 distance from center of rotation to pivot of shoe t ransmit tabIe horsepower moment of friction forces about fixed pivot moment of normal forces about fixed pivot revolutions per minute component along v-axis of forces normal to lining component along w-axis of forces normal to lining pressure between lining and drum maximum Hning pressure
resultant of Nv, Nw, Fv and Fw radius of drum radius to center of gravity of shoe; outer radius of fixed pivot shoe inner radius of fixed pivot shoe distance from center of rotation to fixed pivot reaction along floating link torque about center of rotation weight of shoe inclination of floating link with v-axis inclination of resultant Q with v-axis weight per in.3 inclination of line of maximum pressure with v-axis coefficient of friction angular extent of lining angular velocity before slip occurs, radians/ sec
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(12)
slipping rpm, and the horsepower per shoe. Plot the curve for hp vs n to determine the best value for /x. Solution
Numerical example
By Eq (7)
By Eq (2)
Co py rig hte dM ate ria l
A centrifugal clutch shoe has a radius of 5.25 in. and a width of lining of 2.50 in. Lining pressure is not to exceed 100 psi. Angular length of lining is — 108 deg, and the link is at an angle of a = 48 deg. The shoe is pivoted at a distance h of 4 in. from the center. Total inward spring force of both springs is 15 Ib. Weight of shoe is 3 Ib with its center of gravity at a radius of 4.6 in. As there are linings on the market with a different coefficient of friction, for values of /x of 0.1, 0.2. 0.3, 0.4 and 0.5 find the corresponding values of forces Q, R1 and Fc-Fs. Find the torque T, the corresponding
By Eq (3)
3. Components of resultant force Q
Width b
Spring force
2, Boating-link design
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By Eq (6)
By Eq 4, 5, and 8
From Eq (10) By Eq 9 Then
Co py rig hte dM ate ria l
By Eq 11 and 12
also
The calculations are best carried out in tabular form (see table). Thus, for the case of ^ •= 0.1
Thus
Horsepower
4. Variation of horsepower with coefficient of friction for the floating-link clutch analyzed in the numerical example. Note that best gripping power is obtained with shoe-linings having a coefficient of about 0.35%.
Coefficient of friction, p.
Calculations for various linings
' \x 0.1 0.2 0.3 oX~ 0.5
tan 6
0
Nv
Nir,
0.15112 0.30225
8°35.6' -1840.2 16°49.0' -1774.1
-91.6 -177.3
Fv
Fw
Nv+Fv
N>r.+Fw (N,,-+F1C)-
O
9.2 -184.0 35^5 -354.8
-1831.0 -1738.6
-275.6 -532.1
75,960 1852 283,130 1818
0.45337
24°23.3' -1695.1
-253.1
75.9 -508.5
-1619.2
-761.6
580,030 1789
0.60449
31° 9.2' -1592.7
-317.1
126.8 -637.1
-1465.9
-954.2
910,500 1749
0.75562
37° 4.5' -1484.9
-369.5
184.7 -742.4
-1300.2
-1111.9
1,236,320 1711
[x
tanfi
0.1
0.15052
P " 8°33.6'
R 371
oc-|3
sin (cc-|3) Fr-Fx
39°26.4'
0.63527
1583
T
F0
n,rpm
hp
1102
1598
2019
35.3
1803 '60.8
0.2
0.30605
17° 1.0'
716
30°59.0'
0.51478
1259
2126
1274
0.3
0.47036
25°11.4'
1024
22°48.6'
0.38768
933
3046
948
1556
f
0.25795
607
3817
622
1260 76.3
0.12990
299
4448
314
1011
0.4 ! 0.5
0.65093
33° 3.7'
1284
0.85518
40°32.2V
1496
14°56.3
7°27.8'
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75.2 63.2
S e r r a t e d
C l u t c h e s
a n d
D e t e n t s
L. N. Canick
Fig. I
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(A) Toothed clutch
Driving torque
(B) Detent
Where : m = ratio of tooth thickness to tooth space at radius R n = number of teeth in wheel
I N T H E DESIGN O F straight toothed components such as serrated clutches, Fig. l ( A ) , and detent wheels, Fig. l ( B ) , the effective pitch radius is usually set by size considerations. The torque transmitting capacity of the clutch, or the torque resisting capacity of the detent wheel, is then obtained by assigning suitable values to the engaging force, tooth angle, and coefficient of friction. The nomogram, Fig. 2? is designed to be a convenient means for considering the effect of variations in the values of tooth angle and coefficient of friction. For a given coefficient of friction, there is a tooth angle below which the clutch or detent is self-locking and will transmit torque limited only by its structural strength. Where torque transmitted without clutch slip, or torque resisted by detent wheel, Ib in. effective clutch, or detent wheel, radius, in. axial, or radial, force, Ib tangential force acting at radius R, Ib reaction force of driven tooth, or detent, acting normal to tooth face, Ib
coefficient of friction of tooth material see Fig. l(B) an^le of tooth face, deg
a statement of the conditions of equilibrium for the forces acting on a clutch tooth will lead to the following equation (1
A similar statement of the conditions of equilibrium for the forces acting on a tooth of the detent wheel shown in Fig. l ( B ) will lead to the following equation: (2)
From Eqs (1) and ( 2 ) , when all other terms have constant values, it is obvious that the required axial force, cr the radial force, diminishes as the value of K increases. Dependent upon the values of 0 and ft, the value of K can vary from zero to infinity. The circular nomogram shown in Fig. 2 relates the values of the parameters K. O1 and fx that satisfy the basic equation
Copyright © 2005 by The McGraw-Hill Companies
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EXAMPLE I. Find the maximum tooth angle for a selflocking clutch, or for which K is infinity, taking the coefficient of friction as 0.4 minimum. SOLUTION I. Line I through these values for K and fi on the nomogram gives a maximum tooth angle slightly less than 22 deg for the self-locking condition.
SOLUTION III. Line III through these values for 0 and /A on the nomogram gives a value for K of 0.2. Torque transmitting capacity of flat-face clutch: Torque transmitting capacity of toothed-clutch:
Co py rig hte dM ate ria l
EXAMPLE II. Find the minimum value of K to be expected for a clutch having a tooth angle of 30 deg and a coefficient of friction of 0.2 minimum.
EXAMPLE III. Find the value of K for a flat-face (6 equals 90 deg) friction clutch, the face material of which has a coefficient of friction of 0.2. Compare its torque transmitting capacity with that of the toothed clutch of Example II.
SOLUTION IL Line II through these values for 0 and /x on the nomogram gives a value for K of 3 approximately.
Thus for equal effective radii and engaging forces, the torque capacity of the toothed-clutch is 3/0.2, or 15, times greater than that of the flat face clutch.
Tooth angle, 6
Line IE
Line I
Line IH
Coefficient of friction, u
Fig. 2
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S p r i n g t o
D r i v e
B a n d s
G r i p
T i g h t l y
O v e r r u n n i n g
New spiral-band clutch
C l u t c h
Sprag clutch
Roller clutch
Co py rig hte dM ate ria l
Spiral band
Force here actuates clutch
Spiral-band assembly
Force here releases clutch
Contact area with pulley (typical each clutch band}
Spiral bands direct force inward as outer ring drives counterclockwise. Roller and sprag types direct force outward. Statorconverter
A new type of overrunning clutch that takes up only half the usual space employs a series of spiralwound bands instead of the conventional rollers or sprags to transmit high torques. The new design (drawings, above) also simplifies the assembly, cutting costs as much as 40% by eliminating more than half the parts in conventional clutches. The key to the savings in cost and bulk is the new design's freedom from the need for a hardened outer race. Roller and sprag types must have hardened races because they transmit power by a wedging action between the inner and outer races. Role of spring bands. Overrunning clutches, including the spiralband type, slip and overrun when reversed—in drawing above, when outer member is rotated clockwise and inner ring is the driven member. The new clutch, developed by National Standard Co., Niles, Mich., contains a set of high-carbon springsteel bands (six in the design illustrated) that grip the inner member when the clutch is driving. The outer member merely serves to retain the spring anchors and to play
a part in actuating the clutch. Since it isn't subject to wedging action, it can be made of almost any material, and this accounts for much of the cost saving. For example, in the automotive torque converter in the drawing at right, the bands fit into the aluminum die-cast reactor. Reduced wear. The bands are spring-loaded over the inner member of the clutch, but they are held and rotated by the outer member. The centrifugal force on the bands thus releases much of the force on the inner member and considerably decreases the overrunning torque. Wear is, therefore, greatly reduced. The inner portion of the bands fits into a V-groove in the inner member. When the outer member is reversed, the bands wrap, creating a wedging action in this V-groove. This action is similar to that of a spring clutch with a helical-coil spring, but the spiral-band type has very little unwind before it overruns, compared with the coil type. Thus it responds faster. Edges of the clutch bands carry the entire load, and there is also a compound action of one band upon
Copyright © 2005 by The McGraw-Hill Companies
Clutch-band assembly
Race converter
Spiral clutch bands can be bought separately to fit in user's assembly.
another. As the torque builds up, each band pushes down on the band beneath it, so each tip is forced more firmly into the V-groove. National Standard plans to sell the bands as separate components, without the inner and outer clutch members (which the user customarily builds as part of his product). The bands are rated for torque capacities from 85 to 400 ft.-Ib. Applications include auto transmissions and starters and industrial machinery.
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A c c u r a t e T o r q u e
S o l u t i o n
f o r
D i s k - C l u t c h
C a p a c i t y
Nils M. Sverdrup
IN
COMPUTING
TORQUE
CAPACITY,
T P M R n
Co py rig hte dM ate ria l
the mean radius T^ of the clutch disks is often used. The torque equation then assumes the following form: (D Where = torque, in.-Ib — pressure, Ib. — coefficient of friction = mean radius of disks, in. — no, of friction surfaces
This formula, however, is not mathematically correct and should be used cautiously. The formula's accuracy varies with the ratio D1/D0. When D1ZD0 approaches unity, the error is negligible; but as the value of this ratio decreases, the induced error will increase to a maximum of 33 percent. By introducing a correction factor, <£, Eq (1) can be written (2) The value of the correction factor can be derived by the calculus derivation of Eq (2). Sketch above represents a disk clutch with n friction surfaces, pressure between plates being p psL Inside and outside diameters of effective friction areas are D1 and D0 in., respectively. Since the magnitude of pressure on an element of area, dA, at distance x from center is pdA, the
friction force is pdAfi and the moment of this force around the center is pdAfxx. Integrating within limits D t /2 and D o /2 and multiplying by n friction surfaces, the expression for total torque in in.-Ib is obtained. Hence
If the total pressure acting on clutch disks be P Ib, the expression for pressure per unit area is
Substituting this value for p in Eq (5)
(3)
but
(6)
Now let
(4)
so that.
Substituting in Eq (3)
(7)
Substituting in Eq (6)
or
(5)
(8)
Similarly, by substituting value of D 1 from Eq (7) in Eq ( 2 ) , and having
Correction Foctor <|>
or
(9)
Equating expressions (8) and (9)
and solving for , the result is (10)
D1/D0
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With various diameter ratios, the values for <> / were computed and represented in graph herewith. By using this graph and Eq ( 2 ) , accurate values of torque can be easily determined.
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S p r i n g - L o a d e d i n
O n e - W a y
P i n s
A i d
S p r a g s
C l u t c h SptOQ
Sprags
Co py rig hte dM ate ria l
Sprags combined with cylindrical rollers in a bearing assembly can provide a simple, low-cost method for meeting the torque and bearing requirements of most machine applications. Designed and built by Est. Nicot of Paris, this unit gives onedirection-only torque transmission in an overrunning clutch. In addition, it also serves as a roller bearing. The torque rating of the clutch depends on the number of sprags. A minimum of three, equally spaced around the circumference of the races, is generally necessary to get acceptable distribution of tangential forces on the races.
ftysh pm $prwg
Cylindrical
miters
CfhnijriCQt softer
Pmhpm
Races are concentric; a locking ramp is provided by the sprag profile, which is composed of two nonconcentric curves of different radius. A spring-loaded pin holds the sprag in the locked position until the torque is applied in the running direction. A stock roller bearing cannot be converted because the hard-steel races of the bearing are too brittle to handle the locking impact of the sprag. The sprags and rollers can be mixed to give any desired torque value.
R o l l i n g - T y p e
C l u t c h
This clutch can be adapted for either electrical or mechanical actuation, and will control Vi hp at 1500 rpm with only 7 W of power in the solenoid. The rollers are positioned by a cage (integral with the toothed control wheel —see diagram) between the ID of the driving housing and the cammed hub (integral with the output gear). When the pawl is disengaged, the drag of the housing on the friction spring rotates the cage and wedges the rollers into engagement. This permits the housing to drive the gear through the cam. When the pawl engages the control wheel while the housing is rotating, the friction spring slips inside the housing and the rollers are kicked back, out of engagement. Power is therefore interrupted. According to the manufacturer, Tiltman Langley Ltd, Surrey, England, the unit operated over the full temperature range of -40° to 2000R
M!ah ••••',o-i«fd mite*
A positive drive is provided by this British roller clutch.
C&% Stf-rfttc?
to-* 'sfw! |^S?¥
{kit ^t mt^tf
$t*v*&q
Two-speed operation is provided by the new cam clutch
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This clutch consists of two rotary members (see diagrams), arranged so that the outer (follower) member acts on its pulley only when the inner member is driving. When the outer member is driving, the inner member idles. One application was in a dry-cleaning machine. The clutch functions as an intermediary between an ordinary and a high-speed motor to provide two output speeds that are used alternately.
Source: Mechanisms and Mechanical Devices Sourcebook, 3E, by Chironis & Sclater, © 2001, McGraw-Hill Retrieved from: www.knovel.com
MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
8
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CHAINS, SPROCKETS & RATCHETS Hs itory of Chan is 8-2 n Igeno ius Jobs for Roe lr Chan i 8-4 Bead Chan is for Lg iht Servc ie 8-8 Meh tods for Reducn ig Pus lao tins in Chan i Drv ies 8-10 Lubrc iato in of Roe lr Chan is 8-12 Sheet Metal Gears, Sprockets, Wom r s & Ratchets 8-14 Ratchet Layout Anay lzed 8-16 No Teeth Ratchets 8-18 OneW - ay Drv ie Chan i Sov les Probelm of Sprocket Skp i 8-20
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H i s t o r y
o f
C h a i n s
William R. Edgerton
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The fundamental concept of creating a strong, yet flexible, chain structure by joining together a consecutive series of individual links is an idea that dates back to the earliest human utilization of metals. The use of iron for this purpose probably dates to the eighth century B.C. The second step in the development process was the fashioning of wheels adapted to interact with the flexible chains, by the provision of teeth and pockets on the circumference of the wheels. These specially adapted wheels, known as "sprocket wheels," but usually referred to simply as "sprockets," were first developed by the military engineers of Greece some 22 centuries ago. From the writings of Philo of Byzantium, c. 200 B.C., we learn of chain and sprocket drives being used to transmit power from early water wheels, of a pair of chains fitted with buckets to lift water to higher elevations, and of a pair of reciprocating chain drives which acted as a tension linkage to feed and cock a repeating catapult. The first two of these instances of chain and sprocket interaction probably used simple round-link chain, but the third involved a flat-link chain concept designed by Dionysius of Alexandria while working at the Arsenal at Rhodes. The design conceived by Dionysius employed what is now known as the inverted-tooth chain-sprocket engagement principle, a major advance over the cruder round-link design. Despite its very early origins, rather little practical use was made of chain and sprocket interaction for the transmission of power or the conveyance of materials until the advent of the Industrial Revolution, which took place largely during the nineteenth century. The development of machinery to mechanize textile manufacture, agricultural harvesting, and metalworking manufacturing brought with it a need for the positive transmission of power and accurate timing of motions that only a chain-and-sprocket drive could provide. The earliest sprocket chains manufactured in the United States employed cast components, usually of malleable iron, and many configurations of detachable link chain and pintle chain were produced in large quantities. As the need for higher strength and improved wear resistance became evident, chains employing heat-treated steel components were introduced. The use of rolled or drawn steel as a raw material required manufacturing machinery which provided greater dimensional accuracy than was possible in foundry practice, with the result that certain of the new types of sprocket chains came to be known as "precision chain." This developed somewhat earlier in Great Britain than in the United States, starting with the Slater chain, patented in England in 1864. The Slater design was further refined by Hans Renold with the development of precision roller chain, patented in England in 1880. Chain manufacture in the United States continued to be principally concerned with cast and detachable link designs until the American introduction of the "Safety Bicycle" in 1888. Drop-forged steel versions of the cast detachable chains were first used, then precision steel block chain for bicycle driving, and progressively larger sizes were manufactured in the U.S. as the horseless carriage craze swept the country in the 1890s. Precision inverted-tooth chain, popularly known as "silent chain," was introduced in the late 1890s, with many proprietary styles being developed during the early part of the twentieth century. The first efforts toward standardization of roller chain were begun in the 1920s, resulting in the publication of the first chain standard, American Standard B29a, on July 22, 1930. Since that time, eighteen B29 standards have been developed, covering inverted-tooth chain; detachable chain; pintle and offset-sidebar chains; cast, forged, and combination chains; mill and drag chains; and many other styles.
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There are eighteen American National Standards which relate to the various types of sprocket chains in general use. This family of standards is the result of over 50 years of standardization activity, which had its beginning in the work that led to the publication of American Standard B29a—Roller Chain, Sprockets, and Cutters in 1930. The chain types covered by the current standards are as follows: Precision roller chain Inverted-tooth (or silent) chain Double-pitch roller chain for power transmission Double-pitch roller chain for conveyor usage Steel detachable chain Malleable iron detachable chain Leaf chain Heavy-duty offset-sidebar roller chain Combination chain Steel-bushed rollerless chain Mill chain (H type) Heavy-duty roller-type conveyor chain Mill chain (welded type) Hinge-type flat-top conveyor chain Drag chain (welded type) Agricultural roller chain (A and CA types) Chains for water and sewage treatment plants Drop-forged rivetless chain
Co py rig hte dM ate ria l
ANSI B29.1 ANSI B29.2 ANSI B29.3 ANSI B29.4 ANSI B29.6 ANSI B29.7 ANSIB29.8 ANSI B29.10 ANSI B29.ll ANSI B29.12 ANSI B29.14 ANSI B29.15 ANSI B29.16 ANSI B29.17 ANSI B29.18 ANSI B29.19 ANSI B29.21 ANSI B29.22
The basic size dimension for all types of chain is pitch—the center-to-center distance between two consecutive joints. This dimension ranges from 3Ae in (in the smallest inverted-tooth chain) to 30 in (the largest heavy-duty roller-type conveyor chain).
Chains and sprockets interact with each other to convert linear motion to rotary motion or vice versa, since the chain moves in an essentially straight line between sprockets and moves in a circular path while engaged with each sprocket. A number of tooth-form designs have evolved over the years, but the prerequisite of any tooth form is that it must provide:
1. Smooth engagement and disengagement with the moving chain 2. Distribution of the transmitted load over more than one tooth of the sprocket 3. Accommodation of changes in chain length as the chain elongates as a result of wear during its service life
The sprocket layout is based on the pitch circle, the diameter of which is such that the circle would pass through the center of each of the chain's joints when that joint is engaged with the sprocket. Since each chain link is rigid, the engaged chain forms a polygon whose sides are equal in length to the chain's pitch. The pitch circle of a sprocket, then, is a circle that passes through each corner, or vertex, of the pitch polygon. The calculation of the pitch diameter of a sprocket follows the basic rules of geometry as they apply to pitch and number of teeth. This relationship is simply Pitch diameter =
pitch
s i n ( 1 8 0 7 number
of teeth)
The action of the moving chain as it engages with the rotating sprocket is one of consecutive engagement. Each link must articulate, or swing, through a specific angle to accommodate itself to the pitch polygon, and each link must be completely engaged, or seated, before the next in succession can begin its articulation. Source: Mechanical Components Handbook by Robert O. Parmley ©1985 Copyright © 2005 by The McGraw-Hill Companies
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I n g e n i o u s
J o b s
f o r
R o l l e r
C h a i n
How this low-cost industrial workhorse can be harnessed in a variety of ways to perform tasks other than simply transmitting power.
Co py rig hte dM ate ria l
Peter C. Noy
1 LOW-COST RACK-AND-PINION
device is easily assembled from standard parts.
Rigid support
Standard angle brockets fastened to support
2
AN EXTENSION OF RACKAND-PINION PRINCIPLE—
soldering fixture for noncircular shells. Positive-action cams can be similarly designed. Standard angle brackets attach chain to cam or fixture plate.
Feed fube
Solder feed-roll
•Port with noncircutar periphery ciamped to piote (floots free on drive sprockets).
Torch
Drive sprockets
Drive sprocket
3 CONTROL-CABLE DIRECTION-CHANGER extensively used in aircraft.
180° Link
Cable
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Co py rig hte dM ate ria l
Tipping axis
Channel section
Air or hydroutic cylinder
Rollers
Sprocket
Movement
Load platform
4 TRANSMISSION OF TIPPING OR ROCKING MOTION. Can be combined with previous example (3) to transmit this type of motion to a remote location and around obstructions. Tipping angle should not exceed 40° approx.
5 LIFTING DEVICE is simplified by roller chain.
Dogs on chain feed board into machine
Boards
Chain maintains inward pressure on boards through slip dutch
6 TWO EXAMPLES OF INDEXING AND FEEDING uses of roller chain are shown here in a setup that feeds plywood strips into a brush-making machine. Advantages of roller chain as used here are flexibility and long feed.
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l
Examples of how this low-cost but precision-made product can be arranged to do tasks other than transmit power.
Torque
Workpiece
A
Adjustment holes
Sliding sleeve
Throttle control
1 SIMPLE GOVERNOR—weights can be attached by means of standard brackets to increase response force when rotation speed is slow.
Force
2 WRENCH—pivot A can be adjusted to grip a variety of regularly or irregularly shaped objects.
Feed chute
Workpiece
Plate roller guide
3 SMALL PARTS CAN BE CONVEYED, fed, or oriented between spaces of roller chain.
Guide
Sprocket
Workpiece delivered to assembly station
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Two chains provide clearance for pin
4 CLAMP—toggle action is supplied by two chains, thus clearing pin at fulcrum. Pin
Workpiece
Co py rig hte dM ate ria l
Pin
Force
Handle
Curtain track
5 LIGHT-DUTY TROLLEY CONVEYORS can be made by combining standard rollerchain components with standard curtain-track components. Small gearmotors are used to drive the conveyor.
Curtain
Standard
track
I-beam
trolleys
attachment
Roller (or !odder)
Conveyor
chain
hook
6 SLATTED BELT, made by attaching wood, plastic or metal slats, can serve as adjustable safety guard, conveyor belt, fast-acting security-wicket window.
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B
e
a
d
C
h
a
i
n
s
f
o
r
L
i
g
h
t
S
e
r
v
i
c
e
Bernard Wasko
Co py rig hte dM ate ria l
Pat. Pending
Links
Beads
Slots for finks Conical recesses for beads
Sprocket Beoo
Fig. 1— Misaligned sprockets. NoBparallel planes usually occur when alignment is too expensive to maintain. Bead chain can operate at angles up to 0—20 degrees.
Guide
Large radius
Sprocket
Fig. 2—Details of bead chain and sprocket. Beads of chain seat themselves firmly in conical recesses in the face of sprocket. Links ride freely in slots between recesses in sprocket.
Fig. 3—Skewed shafts normally acquire two sets of spiral gears to bridge space between shafts. Angle misalignment does not interfere with qualified bead chain operation on sprockets.
Fig. 4—Right angle drive does not require idler sprockets to go around corner. Suitable only for very low torque application because of friction drag of bead chain against guide.
Bead dia (in.)
Beads per ft
Max working tenston(lb)
Percent max tension
Table I-Load capacity of bead chains. Capacity varies with bead diameter, chain speed and lubrication
Chain speed, ft/ min
Input shaft Pulley fixed to shaft
Idler sprockets
Continuous chain
Tube
PuIley idling over shaft Fig. 5—Remote control through rigid or flexible tube has almost no backlash and can keep input and output shafts synchronized.
FIg. 6—Linear output from rotary input. Beads prevent slippage and maintain accurate ratio between the input and output displacements.
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Output cylinder (over shaft) Output shaft
Fig. 7—Counter-rotating shafts. Input shaft drives two counter-rotating outputs (shaft and cylinder) through a continuous chain.
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Where torque requirements and operating speeds are low, qualified bead chains offer a quick and economical way to: Couple misaligned shafts; convert from one type of motion to another; counter-rotate shafts; obtain high ratio drives and overload
Co py rig hte dM ate ria l
protection; control switches and serve as mechanical counters.
'Stop pins
Oscillating sprocket
Rotating link
Standard bead sprocket
Spring
V-pulley
Counter
Knob
Fig. 9—Restricted angular motion. Pulley, rotated by knob, slips when limit stop is reached; shafts A and B remain stationary and synchronous.
Fig. 8—Angular oscillations from rotary input. Link makes complete revolutions causing sprocket to oscillate. Spring maintains chain tension.
Fig. 10—Remote control of counter. For applications where counter cannot be coupled directly to shaft, bead chain and sprockets can be used.
Switch
Large bead
Timing motor-
Loose chain
Fig. 11—High-ratio drive less expensive than gear trains. Qualified bead chains and sprockets will transmit power without slippage.
Pivot bar Pivot point Spring
Fig. 12—Timing chain containing large beads at desired intervals operates microswitch. Chain can be lengthened to contain thousands of intervals for complex timing.
Idler sprocket
Output sprocket
Fig. 14—Gear and rack duplicated by chain and two sprockets. Converts linear motion into rotary motion.
Fig. 15 — Overload protection. Shallow sprocket gives positive drive for low loads; slips one bead at a time when overloaded.
Standard sprocket Sprocket with shallow recesses
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Driving shaft
Fig. 13—Conveyor belt composed of multiple chains and sprockets. Tension maintained by pivot bar and spring. Width of belt easily changed.
Spring
Retaining collars
Sheet metal
Bead chain
Fig. 16—Gear segment inexpensively made with bead chain and spring wrapped around edge of sheet metal. Retaining collars keep sheet metal sector from twisting on the shaft.
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M e t h o d s i n
C h a i n
f o r
R e d u c i n g
P u l s a t i o n s
D r i v e s
Pulsations in chain motion created by the chordal action of chain and sprockets can be minimized or avoided by introducing a compensating cyclic motion in driving sprockets. Mechanisms for reducing fluctuating dynamic loads in chain and the pulsations resulting therefrom include non-circular gears, eccentric gears, and cam activated intermediate shafts.
Co py rig hte dM ate ria l
Eugene I. Radzimovsky
Fig. 1—The large cast-tooth non-circular gear, mounted on the chain sprocket shaft, has wavy outline in which number of waves equals number of teeth on sprocket. Pinion has a corresponding noncircular shape. Although requiring special-shaped gears, drive completely equalizes chain pulsations. Fig. 2—This drive has two eccentrically mounted spur pinions (1 and 2). Input power is through belt pulley
keyed to same shaft as pinion 1. Pinion 3 (not shown), keyed to shaft of pinion 2, drives large gear and sprocket. However, mechanism does not completely equalize chain velocity unless the pitch lines of pinions 1 and 2 are non-circular instead of eccentric. Fig. 3—Additional sprocket 2 drives noncircular sprocket 3 through fine-pitch chain 1. This imparts pulsating velocity to shaft 6 and to long-pitch conveyor sprocket 5 through pinion 7 and gear 4. Ratio of the gear pair is made same as number of teeth of spocket 5. SpringSp roc Ae t<
Cham
Input shaft
Fig. 2
Fig. I
Fine pitch roller chain 1
Conveyor chain
Input shaft
Fig. 3
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Co py rig hte dM ate ria l Fine pitch rolier chain 4
Conveyor chain
Input
Input shaft
Reduction gears
Fig. 5
Fig. 4
Chain sprocket
actuated lever and rollers 8 take up slack. Conveyor motion is equalized but mechanism has limited power capacity because pitch of chain 1 must be kept small. Capacity can be increased by using multiple strands of fine-pitch chain.
Fig. 4—Power is transmitted from shaft 2 to sprocket 6 through chain 4, thus imparting a variable velocity to shaft 3, and through it, to the conveyor sprocket 7. Since chain 4 has small pitch and sprocket 5 is relatively large, velocity of 4 is almost constant which induces an almost constant conveyor velocity. Mechanism requires rollers to tighten slack side of chain and has limited power capacity.
Fig* 5—Variable motion to sprocket is produced by disk 3 which supports pin and roller 4, and disk 5 which has a radial slot and is eccentrically mounted on shaft 2. Ratio of rpm of shaft 2 to sprocket equals number of teeth in sprocket. Chain velocity is not completely equalized.
(input shaft)
(cam)\Q
(output shaft) Sprocket
Fig. 6
Fig. 6—Integrated "planetary gear" system (gears 4, 5, 6 and 7) is activated by cam 10 and transmits through shaft 2 a variable velocity to sprocket synchronized with chain pulsations thus completely equalizing chain velocity. The cam 10 rides on a circular idler roller 11; because of the equilibrium of the forces the cam maintains positive contact with the roller. Unit uses standard gears, acts simultaneously as a speed reducer, and can transmit high horsepower. Potent applied tor #425,076
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L u b r i c a t i o n
o f
R o l l e r
C h a i n s
Co py rig hte dM ate ria l
Oil application Bushing
Fig. 2—MANUAL APPLICATION OF LUBRICANT by (A) flared-lip oi! can, or (B) hand brush, is simplest method for low-speed applications not enclosed in casings. New chains should be lubricated daily until sufficiently "broken-in," after which weekly lubrication programs should suffice.
Roller Roller link plate\ Pin link plate Fig. I
Fig. 1—APPLY OIL DROPS between roller and pin links on lower strand of chain just before chain engages sprocket so that centrifugal force carries oil into clearances. Oil applied at center of roller face seldom reaches the area between bushing and roller.
(AJ
(B)
Fig. 2
Light oil
Kerosene or gasoline
(B)
(A)
Fig. 3
(C)
Fig. 3—CHAINS WITHOUT CASING should be: (A) removed periodically and washed in kerosene, (B) soaked in light oil after cleaning, and (C) draped to permit excess oil to drain. Fig. 4—DRIP LUBRICATION can be adjusted to feed oil to edges of link plates at rate of 4 to 20 drops per minute depending on chain speed. Pipe contains oil-soaked wick to feed multiple-width chains.
Fig. 5—CONTINUOUS LUBRICATION systems for open chains: (A) Wick lubrication is lowest in cost to install; (B) Friction wheel lubrication uses wheel covered with soft absorbent material and pressured by flat spring.
Oil cup
Glass sight-
Wick soaked with oil Cut-awoy of pipe
Oil-feed adjuster
Chain
OH reservoir Cross-section of bracket
Wheel Fiat spring
Chain
Wick (A)
Oil reservoir Fig. 5
Fig. 4
(B)
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Unsatisfactory chain life is usually the result of poor or ineffective lubrication. damage is caused by faulty lubrication than by years of normal service.
More
Illustrated
below are 9 methods for lubricating roller chains. Selection should be made on basis of chain speed as shown in Table I . Recommended
Table I—Recommended Methods
lubricants are listed in Table I I .
Lubricants
Co py rig hte dM ate ria l
Table II—Recommended
Chain Speed, ft/min 0-600
Pitch of chain, in.
Method
Manual: brush, oil can Slow Drip: 4-10 drops,min Continuous: wick, wheel
600-1500
Rapid Drip—20 drops ,min Shallow Bath, Disk
over 1500
Force Feed Systems
Viscosity at 100 F, SUS
1
A-Vs
Z
A~\YA
lJ/2-up
SAE No.
240-420
20
420-620
30
620-1300
40
Note: For ambient temperatures between 100 to 500 F use SAE SO.
Fig. 6—SHALLOW BATH LUBRICATION uses casing as reservoir for oil. Lower part of chain just skims through oil pool. Levels of oil must be kept tangent to chain sprocket to avoid excessive churning. Should not be used at high speeds because of tendency to generate excessive heat.
Baffle
Disk
Chain
Sprocket
Gutter
Fig. 7
Oil reservoir
Fig. 6
Fig. 7—DISK OR SLEVGER can be attached to lower sprocket to give continuous supply of oil. Disk scoops up oil from reservoir and throws it against baffle. Gutter catches oil dripping down from baffle and directs it on to chain.
Oil gage Oil
-Drain plug
Fig. 8—FORCE-FEED LUBRICATION for chains running at extremely high speeds. Pump driven by motor delivers oil under pressure to nozzles that direct spray on to chain. Excess oil collects in reservoir which has wide area to cool oil. Spray nozzles
Chain
Flow control valve
Drive shaft
Pump chain
Pump Flexible hose
Fig. 8
Inlet
MotorOil pump
Oil reservoir
Excess oil Oil reservoir
Fig. 9
Fig. 9—CHAIN-DRIVEN FORCE-FEED system has pump driyen by main drive shaft. Flow control valve, regulated from outside of casing, by-passes excess oil back to reservoir. Inlet hose contains filter. Oil should be changed periodically—especially when hue is brown instead of black.
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S h e e t
M e t a l
W o r m s
&
G e a r s ,
S p r o c k e t s ,
R a t c h e t s
Haim Murro
Pinion
Co py rig hte dM ate ria l
When a specified motion must be transmitted at intervals rather than continuously, and the loads are light, these mechanisms are ideal because of their low cost and adaptability to mass production. Although not generally considered precision parts, ratchets and gears can be stamped to tolerances of ±0.007 in. and if necessary, shaved to closer dimensions. Sketches indicate some variations used on toys, household appliances and automobile components.
Fig I Gear
Fig.2
Fig. 3
Fig.4
Prong
Fig. 1—Pinion is a sheet metal cup, with rectangular holes serving as teeth. Meshing gear is sheet metal, blanked with specially formed teeth. Pinion can be attached to another sheet metal wheel by prongs, as shown, to form a gear train.
Fig. 3—Pinion mates with round pins in circular disk made of metal, plastic or wood. Pins can be attached by staking or with threaded fasteners.
Fig. 2—Sheet metal wheel gear meshes with a wide face pinion, which is either extruded or machined. Wheel is blanked with teeth of conventional form.
Fig. 4—Two blanked gears, conically formed after blanking, make bevel gears meshing on parallel axis. Both have specially formed teeth.
No. 2
Fig.5
Fig.6
Fig. 5—Wheel with waves on its outer rim to replace teeth, meshes with either one or two (shown) sheet metal pinions, having specially formed teeth, and mounted on intersecting axes.
Fig. 6—Two bevel type gears, with specially formed teeth, mounted for 90 deg intersecting axes. Can be attached economically by staking to hubs.
Fig. 7
Fig.8
Gear NoI
No.?
Fig.9
Fig. 7—Blanked and formed bevel type gear meshes with solid machined or extruded pinion. Conventional form of teeth can be used on both gear and pinion. Fig. 8—Blanked, cup-shaped wheel meshes with solid pinion for 90 deg intersecting axes. Fig. 9—Backlash can be eliminated from stamped gears by stacking two identical gears and displacing them by one tooth. Spring then bears one projection on each gear taking up lost motion.
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Co py rig hte dM ate ria l Worm wheel
Fig. 11—Blanked wheel, with specially formed teeth, meshes with a helical spring mounted on a shaft, which serves as the worm.
Fig. 10—Sheet metal cup which has indentations that take place of worm wheel teeth, meshes with a standard coarse thread screw.
Fig.12
Fig.Il
Fig.iO
Fig. 12—Worm wheel is sheet metal blanked, with specially formed teethWorm is made of sheet metal disk, split and helically formed.
Fig. 13—Blanked ratchets with one sided teeth stacked to fit a wide, sheet metal finger when single thickness is not adequate. Ratchet gears can be spot welded. Fig. 14—To avoid stacking, single ratchet is used with a U-shaped finger also made of sheet metal.
Fig. 15
Fig. 13
Fig. 15—Wheel is a punched disk with square punched holes to selve as teeth. Pawl is spring steel.
Fig.14
Fig. 16 Fig.17 Fig. 16—Sheet metal blanked pinion, with specially formed teeth, meshes with windows blanked in a sheet metal cylinder, to form a pinion and rack assembly.
Fig.18 Fig. i7_Sprocket, like Fig. 13, can be fabricated from separate stampings. Fig, 18—For a wire chain as shown, sprocket is made by bending out punched teeth on a drawn cup.
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R a t c h e t
L a y o u t
A n a l y z e d
Here, in a brief but comprehensive rundown, are generally unavailable formulas and data for precise ratchet layout.
Co py rig hte dM ate ria l
Emery E. Rossner
Symbols
moment arm of wheel torque moment about Oi caused by weight of pawl ratchet and pawl pivot centers respectively • tooth pressure = wheel torque/a load on pivot pin friction coefficients Other symbols as defined in diagrams
Pawl in compression . • . has tooth pressure P and weight of pawl producing a moment that tends to engage pawl. Friction-force fiP and pivot friction tend to oppose pawl engagement.
The ratchet wheel is widely used in machinery, mainly to transmit intermittent motion or to allow shaft rotation in one direction only. Ratchet-wheel teeth can be either on the perimeter of a disc or on the inner edge of a ring. The pawl, which engages the ratchet teeth, is a beam pivoted at one end; the other end is shaped to fit the ratchet-tooth flank. Usually a spring or counterweight maintains constant contact between wheel and pawl. It is desirable in most designs to keep the spring force low. It should be just enough to overcome the separation forces—inertia, weight and pivot friction. Excess spring force should not be relied on to bring about and maintain pawl engagement against the load.
To insure that the pawl is automatically pulled in and kept in engagement independently of the spring, a properly Iayed out tooth flank is necessary. The requirement for self-engagement is Neglecting weight and pivot friction
or but c/b — r/a = tan , and since tan <£ is approximately equal to sin <j> Substituting in term (1)
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Co py rig hte dM ate ria l
Paw! in tension . . . has same forces acting on unit as other arrangements. Same layout principles apply also.
Inner teeth . . . allow compact assembly of pawl and ratchet.
For steel on steel, dry, p = 0,15. Therefore, using
the margin of safety is large; the pawl will slide into engagement easily. For internal teeth with <j> of 30 °, c/b is tan 30° or 0.577 which is larger than ^, and the teeth are therefore self engaging. When laying out the ratchet wheel and pawl, locate points Oy A and O1 on the same circle. AO and AOi will then be perpendicular to one another; this will
insure that the smallest forces are acting on the system. Ratchet and pawl dimensions are governed by design sizes and stress. If the tooth, and thus pitch, must be larger than required in order to be strong enough, a multiple pawl arrangement can be used. The pawls can be arranged so that one of them will engage the ratchet after a rotation of less than the pitch. A fine feed can be obtained by placing a number of pawls side by side, with the corresponding iatchct wheels uniformly displaced and interconnected.
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N o
T e e t h
R a t c h e t s
With springs, rollers and other devices they keep going one way.
Co py rig hte dM ate ria l
L. Kasper
Supporting stud
Swinging powis
Hole for spring fang
Spring
1
Pawl
2
1 SWINGING PAWLS lock on rim when lever swings forward, and release on return stroke. Oversize holes for supporting stud make sure both top and bottom surfaces of pawls make contact.
Sheave
2 HELICAL SPRING grips shaft because its inner diameter is smaller than the outer diameter of shaft. During forward stroke, spring winds tighter; during return stroke, it expands. 3 V-BELT SHEAVE is pushed around when pawl wedges in groove. For a snug fit, bottom of pawl is tapered like a V-belt.
3
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Spring
Rollers
Gear-
Rack
Pin Threaded hub
Co py rig hte dM ate ria l
Cross piece
Lever
Conicolplate
6
4
5
Drum
Flat springs
Disk,
Eccentric com
Elongatedhole
8
7
4 ECCENTRIC ROLLERS squeeze disk on forward stroke. On return stroke, rollers rotate backwards and release their grip. Springs keep rollers in contact with disk.
5 RACK is wedge-shape so that it jams between the rolling gear and the disk, pushing the shaft forward. When the driving lever makes its return stroke, it carries along the unattached rack by the crosspiece.
6 CONICAL PLATE moves as a nut back and forth along the threaded center hub of the lever. Light friction of springloaded pins keeps the plate from rotating with the hub. 7 FLAT SPRINGS expand against inside of drum when lever moves one way, but drag loosely when lever turns drum in opposite direction. 8 ECCENTRIC CAM jams against disk during motion half of cycle. Elongated holes in the levers allow cam to wedge itself more tightly in place.
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O n e - W a y o f
D r i v e
S p r o c k e t
C h a i n
S o l v e s
S k i p
Roller
Pull
Sprocket
Pin
Double or nothing—that's the principle Milton Morse, president of APM Hexseal Corp., Englewood, N. J., followed when he developed his grease-free, skip-free, Kleenchain drive-chain for bicycles. And depending upon the way it is used, it can be either the best chain drive or the worst. Morse uses it the best way and plans to make it available soon. Alternate pairs of side plates "B" (drawing left) are attached to bushings and are carried within sideplates "A." These outer side-plates are secured in pairs to pins that are carried, but still free to move in the bushings. The bushings also carry rollers that contact, and tend to rotate with, the sprocket teeth. But it is this tendency for the bushings to rotate, plus the friction between the roller and the bushing when the chain is under tension, that causes the chain to rise and skip over sprocket teeth in conventional design. This condition occurs only on alternate teeth where pin-supported side-plates are applying tension to the chain. The adjacent bushing-supported side plate is forced to roll on the tooth and rise as the bushing is squeezed between roller and pin. No-skip link. On the next tooth, bushing-supported side-plates are transferring the tension to the chain and only the roller is squeezed— this time between the tooth and the bushing. The pins supporting the link following are not under pressure and are free to let the approaching links drape in the ideal manner around the sprocket. Regardless of how small the sprocket is, the chain will not attempt to skip. Morse's chain doesn't skip, because he made it out of only one type of link, by using offset links (drawing left). One end of the side-plates is connected to bushings, and the other is connected to pins. If the chain is applied so the tension is transferred to the tooth only by bushings, the adjacent link will always be pin-supported, and the chain will drape freely around the smallest sprocket. By using smaller sprockets, it is possible to make larger reductions with fewer stages.
Co py rig hte dM ate ria l
Side-plate B Bushing
P r o b l e m
Side-plate A
Link can skip a tooth in conventional chain (above), because tension on chain squeezes bushing, which forces next link to rotate and rise. But if all links are offset (below) and chain is properly applied, it will drape freely around sprockets.
Off-set side-plate
PuIt
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
9
Co py rig hte dM ate ria l
BELTS & BELTING Ten Types of Betl Drv ies Fn id the Lengh t of Open and Co lsed Betls Getn ig in Step wtih Hybrd i Betls Equao itns for Compun itg Creep in Betl Drv ies Mechansims for Adu jsn tig Tenso in of Betl Drv ies Leather Bets l-Hp Loss and Speeds
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9-2 9-4 9-6
9-10 9-14 9-16
T e n
T y p e s
o f
B e l t
D r i v e s
Although countless types of belt drives are possible, these ten will solve most industrial applications. These pertain to power transmission only; the tooth type of timing belt is not included. For each drive are given: design pitfalls; speed and capacity ranges; and suggestions for application.
(A)
Co py rig hte dM ate ria l
George R. Lederer
Fig. I OPEN DRIVE (V, Flat or Poly V Belts)
(B)
Fig. 2 THREE PULLEY DRIVE (V1 Rot or Pofy V Beits)
Fig.4 REVERSE BEND IDLER ( Poly V, V, or Flat Belts)
FIG. 1—Can be either horizontal ( A), or vertical (B). Used on equipment ranging from washing machines to oil well pumps. Ideal for high capacity drives; allows wider range of speed ratios than any other type. Provisions must be made for takeup. No minimum or maximum center distance limits other than available belt lengths. FIG. 2—Limited in capacity to 8-10 hp because of small high-speed pulleys and limited provisions for take-up. Usually used with one unit hingemounted, as in automotive fan belt drives. Large belts would stretch beyond capacity of hinged unit to take up slack. FIG. 3—Useful where several units are driven from a central shaft. The Vv belt that resembles two v-belts joined back-to-back was developed especially for this drive. For Vv operation all pulleys must be grooved. For regular V-, PoIy-V or flat-belt operation, only those driven by the belt face are grooved, others are flat and are driven by the back of the belt. Driving capacity range from 15-25 hp. Sheaves are small, speed is slow and belt flex is extremely high, which affects belt life. FIG. 4—Used where driver and driven sheaves are fixed and there is no provision for take-up. Idler
Fig.3 SERPENTINE DRIVE (Poly V,V1 or Flat Belts)
is placed on the slack side of the belt near the point where the belt leaves the driver sheave. Idler also gives increased wrap and increased arc of contact. Applications range from agricultural jackshaft drives to machine tools and large oil field drives. Idler can be spring loaded to keep belt tight if drive is subject to shock. For maximum belt life, the larger the idler, the better.
FIG. 5—Driver and driven sheaves are at right angles; belt must travel around horizontal sheave, turn, go over vertical sheave and return. Bend must be gradual to prevent belt from leaving sheave. Minimum center distance for V-belts is 5-5 in. X (pitch dia of largest sheave + width of sheave). For PoIy-V, minimum center distance = 13 X pitch dia of small sheave or 5.5 X (pitch dia -f belt width). For flat belts it is 8 X
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Co py rig hte dM ate ria l
Fig.6 QUARTER-TURN DRIVE (REVERSE BENDIDLER) (Poly V,V,or Flot Belts)
Fig. 5 QUARTER-TURN DRIVE (OPEN) (Poly V1V, or Plot Belts)
Fig.7 CROSSED BELT DRIVE (Flat Only)
Fig. 8 ANGLE DRIVE (EIGHTH TURN) (Poly V,V, or Flat Belts)
(pitch dia -f- width). V-belt sheaves must be deep grooved and close matching is essential. Speed usually ranges from 3,000-5,000 rpm; hp from 75-150.
Fig.9 MULE DRIVE (Poly V, V,or Rot Belts)
FIG. 6—Similar to Open Quarter-Turn but has higher capacity with shorter centers and increased wrap. Tracking is a problem with fiat belts. With PoIy-V drive, speed ratio is unlimited. Angle of entry (angle between belt and a line perpendicular to face of the sheave) is limited to 3 deg or less. FIG. 7—Limited to flat belts because either V-belt or PoIy-V would rub against itself and burn or wear rapidly. Desirable only where the direction of rotation must be reversed such as on planers, woodworking tools in general and line shaft drives.
FIG. 8—Used where driver and driven sheave cannot be on the same plane. Has same center distance and angle of belt entry limitations as Quarter-Turn. Drive can be open if take-up can be accomplished at either end or it can be fitted with a reverse bend idler, but not an inside idler. Angle between shaft can be from zero to 90 deg.
FIG. 9—Especially developed for drill presses and special applications where driver and driven sheaves are at right angles to each other and yet on the same plane. Can operate around a corner or from one floor to another. The center sheave is 90 deg from the driver and driven sheave and acts as an idler. Twists affect belt life.
Fig. 10 VARIABLE SPEED DRIVE (V Belts Only)
FIG. 10—Sheaves must be grooved to change the pitch diameter for variable or adjustable pitch operation. With two sheaves and one belt, it is possible to have a range of four different speeds. Widely used on propulsion drives and cylinder drives on agricultural combines and machine tools. Drive has same high capacity and advantage as standard open drive, with wider speed range. They are mostly single belt drives VA to 2 in. wide. Small pulleys are not advisable. Most applications require special vari-speed cylinder or traction belt.
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a n d
t h e
L e n g t h
C l o s e d
o f
O p e n
B e l t s
The following formulas give the answers (see the illustrations for notation): Open length, L = nD + (tan $ — B) (D — d) Closed length, L == (D + d) U + (/an 6 — B)] You can find 6 from (for open belts): cos $ = (D — d)/2C;
(for closed belts)
cos 9 = (D + d)/2C.
Co py rig hte dM ate ria l
F i n d
When you want to find the center distance of belt drives, however, it is much quicker if you have a table that gives you y = cos 6 in terms of x — (tan 0) — 0. Sidney Kravitz, of Picatinny Arsenal, has compiled such a table. Now, all you need do to find C is first calculate x ~ [L/(D + d)] — ir for open drives.
y values 1
y
x
(see note below for x > 100) then If JC > 100, calculate C from C = » - ^ (D + d) for both open and closed belts. Copyright © 2005 by The McGraw-Hill Companies
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for closed drives Then
Co py rig hte dM ate ria l
for open drives
for closed drives
Example: L = 60.0, D = 15.0, d = 10.0, x = (L — vD)/(D - ^) = 2,575, y = 0.24874 by linear interpolation in the table. C = (D - d)/2y = 10.051, •
•
•
•
Morton P. Matthew's letter on fractional derivatives (PE—July 22 '63, p 105) drew several interesting comments from readers. Here's what Professor Komkov of the University of Utah had to say on the subject. He pointed out that the question raised by Mr. Matthew is well known in mathematics, but very little publicized. "The definition of fractional derivatives goes back to Abel, who developed around 1840 this fascinating little formula:
(r (n) is the Euler's Gamma Function). An elementary proof of this formula is given for example in Courant's Differential and Integral Calculus, Part II, page 340. Abel claimed that the formula works for all real values of 5, although there is no guarantee that the range of values obtained can be bounded. For a negative S Abel's operator D* becomes an integral operator:
All results quoted by Mr Matthew may be easily obtained by application of Abel's Formula. "There exists a generalization to partial differential equations of the fractional derivative. This is the so-called Riesz Operator. In one dimensional case it becomes Abel's derivative of fractional order. "Details of the Riesz technique are explained, for example, in Chapter 10 of Partial Differential Equations by Duff. Unfortunately I know of no textbook which devotes more than a few pages to the subject of fractional derivatives. However, there exists a large number of papers on the subject in mathematical journals. I remember reading one by Professor John Barrett in the Pacific Journal of Mathematics (I think it was 1947) which discussed the equation:
"There are some interesting applications in engineering and science for this theory. I was interested some years ago in formulation of elasticity equations for some plastics. I have never completed that investigation but I have established that in some cases, the behavior of plastics may be better simulated by assuming stress-strain relationship to be of the type:
where s is some number between 0 and 1, than by the usual assumption of linear superposition of Hooke's law and Newtonian Fluid properties. In case of some rubbers s worked to be close to 0.7." Copyright © 2005 by The McGraw-Hill Companies
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G e t t i n g
i n
S t e p
w i t h
H y b r i d
B e l t s
Imaginative fusions of belts, cables, gears and chains are expanding the horizons for light-duty synchronous drives
Co py rig hte dM ate ria l
Belts have long been used for the transfer of mechanical power. Today's familiar flat belts and V-belts are relatively light, quiet, inexpensive, and tolerant of alignment errors. They transmit power solely through factional contacts. However, they function best at moderate speeds (4000 to 6000 fpm) under static loads. Their efficiencies drop slightly at low speeds, and centrifugal effects limit their capacities at high speeds. Moreover, they are inclined to sip under shock loads or when starting and braking. Even under constant rotation, standard belts tend to creep. Thus, these drives must be kept under tension to function properly, increasing loads on pulley shaft bearings. Gears and chains, on the other hand, transmit power through bearing forces between positively engaged surfaces. They do not slip or creep, as measured by the relative motions of the driving and driven shafts. But the contacts themselves can slip significantly as the chain rollers and gear teeth move in and out of mesh. Positive drives are also very sensitive to the geometries of the mating surfaces. A gear's load is borne by one or two teeth, thus magnifying small tooth-totooth errors. A chain's load is more widely distributed, but chordal variations in the driving wheel's effective radius produce small oscillations in the chain's velocity. To withstand these stresses, chains and gears must be carefully made from hard materials and must then be lubri-
Circular
pitch
A
Tooth
Backing
cord
Facing
A
Pulley face
radius
Pulley pitch
radius
Tension member
A-A Cross-section
Fig. 1 Conventional timing belts have fiberglass or polyester tension members, bodies of neoprene or polyurethane, and trapezoidal tooth profiles.
Belt
Driven
A
sprocket
Rods Driving
sprocket
Rods
Tooth^
Wires
Driven
B
Driving
Connecting
Noise suppressing layer
sprockei
sprocket
Continuous
belt
Fig. 2 NASA metal timing belts exploit stainless steel's strength and flexibility, and are coated with sound-and friction-reducing plastic.
Source: Mechanisms and Mechanical Devices Sourcebook, 3E, by Chironis & Sclater, © 2001 McGraw-Hill Copyright © 2005 by The McGraw-Hill Companies
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cated in operations. Nevertheless, their operating noise betrays sharp impacts and friction between mating surfaces. The cogged timing belt, with its trapezoidal teeth (Fig. 1), is the best-known fusion of belt, gear, and chain. Though these well-established timing belts can handle high powers (up to 800 hp), many of the newer ideas in synchronous belting have been incorporated into low and fractional horsepower drives for instruments and business machines.
Bead chain' Conical recesses
Steel cable
Bead
Polyurethane coating
Sprocket Slots for cable A
Co py rig hte dM ate ria l
fdiers
Steel Belts for Reliability
Researchers at NASA's Goddard Space Flight Center (Greenbelt, MD) turned to steel in the construction of long-lived toothed transmission belts for spacecraft instrument drives. The NASA engineers looked for a belt design that would retain its strength and hold together for long periods of sustained or intermittent operation in hostile environments, including extremes of heat and cold. Two steel designs emerged. In the more chain-like version (Fig. 2A), wires running along the length of the belt are wrapped at intervals around heavier rods running across the belt. The rods do double duty, serving as link pins and as teeth that mesh with cylindrical recesses cut into the sprocket. The assembled belt is coated with plastic to reduce noise and wear. In the second design (Fig. 2B), a strip of steel is bent into a series of U-shaped teeth. The steel is supple enough to flex as it runs around the sprocket with its protruding transverse ridges, but the material resists stretching. This belt, too, is plastic-coated to reduce wear and noise. The V-belt is best formed from a continuous strip of stainless steel "not much thicker than a razor blade," according to the agency, but a variation can be made by welding several segments together. NASA has patented both belts, which are now available for commercial licensing. Researchers predict that they will be particularly useful in machines that must be dismantled to uncover the belt pulleys, in permanently encased machines, and in machines installed in remote places. In addition, stainless-steel belts might find a place in high-precision instrument drives because they neither stretch nor slip. Though plastic-and-cable belts don't have the strength or durability of the NASA steel belts, they do offer versatility and production-line economy. One of the least expensive and most adaptable is
Largeradius guide
B
C
D
E
Input shaft
Switch
Large bead
Tube
F
Driving pulley Continuous chain
Output cylinder {over shaft)
Timing motor
idler
G
Loose chain
H
Stop pins
Oscillating sprocket
Output shaft
I
Spring
Bead sprocket
Pivot
A
Spring
B
V-pulley
Metai ptate
J
Rotating fink
K
L
Knob
Bead chain
Fig. 3 Polyurethane-coated steel-cable "chains"—both beaded and 4-pinned—can cope with conditions unsuitable for most conventional belts and chains.
Table 1 . Conventional Timing Belts Type
Circular pitch, in.
Wkg. tension Ib/in. width
Centr. loss const., K0
0.080 0.200 0.376 0.500 0.0816
32 41 55 140 13
10 x 10~9 27 x 10-9 38 x 10-9 53 x 10-*
High-torque (Fig 7) 3 mm 0.1181 5 mm 0.1968 8 mm 0.3150
60 100 138
Standard (Fig 1) MXL XL L H 40DP
Copyright © 2005 by The McGraw-Hill Companies
15 x 10-9 21 x 10-* 34 x 10~9 Courtesy Stock Drive Products
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Pinned beads and belts
Stainless
steel core
Gear meshing with sprocket
Poiyurethane jacket
• • Pinned beads
Co py rig hte dM ate ria l
Aramid fiber core
in different planes, the bead chain can compensate for up to 20° of misalignment (Fig. 3C). Skewed shafts, up to 90° out of phase (Fig. 3D). Right-angle and remote drives using guides or tubes (Figs. 3E and 3F). These methods are suitable only for low-speed, low-torque applications. Otherwise, frictional losses between the guide and the chain are unacceptable. Mechanical timing, using oversize beads at intervals to trip a microswitch (Fig. 3G). The chain can be altered or exchanged to give different timing schemes. Accurate rotary-to-linear motion conversion (Fig. 3H). Driving two counter-rotating outputs from a single input, using just a single belt (Fig. 31). Rotary-to-oscillatory motion conversion (Fig. 3J). Clutched adjustment (Fig. 3K). A regular V-belt pulley without recesses permits the chain to slip when it reaches a pre-set limit. At the same time, bead-pulleys keep the output shafts synchronized. Similarly, a pulley or sprocket with shallow recesses permits the chain to slip one bead at a time when overloaded. Inexpensive "gears" or gear segments fashioned by wrapping a bead chain round the perimeter of a disk or solid arc of sheet metal (Fig. 3L). The sprocket then acts as a pinion. (Other designs are better for gear fabrication.)
•
Pinned belt
2-axis pinned chain
Fig. 4 Plastic pins eliminate the bead chain's tendency to cam out of puiiey recesses, and permit greater precision in angular transmission.
the modern version of the bead chain, now common only in key chains and light-switch pull-cords. The modern bead chain—if chain is the proper word—has no links. It has, instead, a continuous cable of stainless steel or aramid fiber which is covered with polyurethane. At controlled intervals, the plastic coating is molded into a bead (Fig. 3A). The length of the pitches thus formed can be controlled to within 0.001 in. In operation, the cable runs in a grooved pulley; the beads seat in conical recesses in the pulley face. The flexibility, axial symmetry, and positive drive of
•
•
bead chain suit a number of applications, both common and uncommon:
•
• An inexpensive, high-ratio drive that resists slipping and requires no lubrication (Fig. 3B). As with other chains and belts, the bead chain's capacity is limited by its total tensile strength (typically 40 to 80 Ib for a single-strand steelcable chain), by the speed-change ratio, and by the radii of the sprockets or pulleys. • Connecting misaligned sprockets. If there is play in the sprockets, or if the sprockets are parallel but lie
•
Ladder chain differential drive
•
A More Stable Approach
Print disk and sprockets
Step motor
Step motor
Ladder chain
Fig. 5 A plastic-and-cable ladder chain in an impact-printer drive, in extreme conditions, such hybrids can serve many times longer than steel.
Copyright © 2005 by The McGraw-Hill Companies
Unfortunately, bead chains tend to cam out of deep sprocket recesses under high loads. In its first evolutionary step, the simple spherical bead grew limbs—two pins projecting at right angles to the cable axis (Fig. 4). The pulley or sprocket looks like a spur gear grooved to accommodate the belt; in fact, the pulley can mesh with a conventional spur gear of proper pitch. Versions of the belt are also available with two sets of pins, one projecting vertically and the other horizontally. This arrangement permits the device to drive a series of perpendicular shafts without twisting the cable, like a bead chain but without the bead chain's load limitations. Reducing twist increases the transmission's lifetime and reliability.
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These belt-cable-chain hybrids can be sized and connected in the field, using metal crimp-collars. However, nonfactory splices generally reduce the cable's tensile strength by half. Parallel-Cable Drives
Co py rig hte dM ate ria l
Another species of positive-drive belt uses parallel cables, sacrificing some flexibility for improved stability and greater strength. Here, the cables are connected by rungs molded into the plastic coating, giving the appearance of a ladder (Fig. 6). This "ladder chain" also meshes with toothed pulleys, which need not be grooved. A cable-and-plastic ladder chain is the basis for the differential drive system in a Hewlett-Packard impact printer (Fig. 5). When the motors rotate in the same direction at the same speed, the carriage moves to the right or left. When they rotate in opposite directions, but at the same speed, the carriage remains stationary and the print-disk rotates. A differential motion of the motors produces a combined translation and rotation of the print-disk. The hybrid ladder chain is also well suited to laboratory of large spur gears from metal plates or pulleys (Fig. 6). Such a "gear" can run quietly in mesh with a pulley or a standard gear pinion of the proper pitch. Another type of parallel-cable "chain," which mimics the standard chain, weighs just 1.2 oz/ft, requires no lubrication, and runs almost silently.
Driving gear
Retaining ring
Milled plate
Fig. 6 A gear chain can function as a ladder chain, as a wide V-belt, or, as here, a gear surrogate meshing with a standard pinion. High-torque (HTD) timing belt
Fig. 7 Curved high-torque tooth profiles (just introduced in 3-mm and 5-mm pitches) increase load capacity of finepitch neoprene belts.
A Traditional Note
A new high-capacity tooth profile has been tested on conventional cogged belts. It has a standard cord and elastic body construction, but instead of the usual trapezoid, it has curved teeth (Fig. 7). Both 3-mm and 5-mm pitch versions have been introduced.
Copyright © 2005 by The McGraw-Hill Companies
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E q u a t i o n s i n
B e l t
f o r
C o m p u t i n g
C r e e p
D r i v e s
Don't confuse slippage caused by overloading with creep found in all belt drives. These equations give the creep rate and power loss in various pulley systems.
Co py rig hte dM ate ria l
Peter L. Garrett
p. = coefficient of friction $ = angle of wrap, radians For velocities substantially below the tension T2 on the slack side. This the speed of sound this equation has is due to friction between belt and been confirmed by tests. For those pulley. By the rules of equilibrium, sufficiently curious to note the effect the maximum possible tension ratio, of extremely high speeds, Eq 1 can TJ T2t that can be transmitted without be modified to include the Mach slip is given by the following equation number, M. (refer to figure below):
HEN a belt is transmitting W power there exists a tension T on the tight side that is greater than
1
(1)
where Tx — tension at tight side, Ib T2 — tension at slack side, Ib e rr natural logarithm base = 2.718
are listed in the table of belt and rope properties on page 89. The relationship between the driving torque, r, and the belt tension is T = (T1
-
T2)RB
(2)
where RB = radius of pulley B plus one half the belt thickness. Therefore, the initial belt tension and ratio T1ZT2 can be increased to prevent slip without affecting the (IA) torque equation (or, more specifically, the difference in tensions, T1 — T2). The limiting factors in this case are Any load greater than t11* in Eq 1 the belt stress and bearing loads. will cause belt slippage, loss of synYet even when there is no slip the chronism and serious wear. Coeffi- belt inexorably creeps backward over cients of friction for belts and ropes the pulleys, an effect that is particu-
Slack side
Driving pulley, A
Tight side DUAL-PULLEY DRIVE
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-Driven pulley, B
Iarly obvious if the drive never reverses. For zero slip, one revolution of pulley A will pull 2TTRA inches of belt at tension T1. However, as the belt approaches point 1, the tension drops to a lower value, T2, and the belt contracts by an amount d equal to
where A — area of belt cross section, in.2 L — segment of belt length, in. E = modulus of elasticity, psi F = tensile loading UL=I in., then
and of the slack side
(5)
Hence
K = AE or
(3)
Co py rig hte dM ate ria l
where K — spring constant of belt. Typical K values are included in the table of properties on page 89. This change in length causes localized slippage between belt and pulley with consequent power dissipation. Thus, pulley A unwinds only (2TTRA — d) inches of belt per revolution, and the belt creeps backward an amount equal to d inches each revolution.
For laminated belts, the calculations are more complex. Belt manufacturers usually can give you the K factor for a belt, but it is a simple matter to obtain the value by test if they do not. For example, 30 in. of belting elongates Vs in. under a 20-lb load. What is the K factor? o,
. deflection Strain = —; r,— length
The K factors Factor J^ in Eq 3 is the spring constant of the belt in units of force per unit strain. Thus
These units for K simplify calculations with belts of different length. The K factor is constant for all belts of a particular material and cross section. It can be calculated easily for belts of uniform material and measurable section. For example, for a steel band with a VA X 0.020-in. cross section
(6)
Velocity V1 can be considered as the nominal belt velocity, and V2 as being equal to V1 minus the creep rate, or
(7)
where creep factor, C, is the fractional loss in speed due to elastic effects. Combining Eq 6 and 7 gives
Velocity relationships
Returning to Eq 3, this relationship can be put into terms of velocity. During a specific time, Ar, pulley A will have rotated through an angular displacement of 0A. Hence the velocity of the tight side is
Since the torque load is equal to
T
= (T1-
T2)R8, then
(4)
Idler (no friction}-
Driving pulley
MULTIPLE-PULLEY DRIVE
Copyright © 2005 by The McGraw-Hill Companies
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(9)
SYMBOLS TIME, SEC TENSION, LB LINEAR VELOCITY OF BELT, IN./SEC CREEP RATE, IN./SEC ANGLE OF WRAP, RADIANS FINITE ANGULAR DISPLACEMENT, RADIANS TORQUE OF LOAD, LB-IN. FRICTION COEFFICIENT
Driver
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CREEP FACTOR, DIMENSIONLESS CHANGE IN BELT LENGTH, IN. SPRING CONSTANT OF BELT, LB/ON./IN.) SEGMENT OF BELT LENGTH, IN. MACH NUMBER-THE RATIO OF THE VELOCITY OF A MOVING BODY TO THAT OF SOUND POWER, LB-IN./SEC. PULLEY RADIUS + 1Z2 BELT THICKNESS, IN.
Steel tape 0,020in. (x-L in.)
SUBSCRIPTS A, B, AND C REFER TO PULLEYS A, BV AND C, RESPECTIVELY.
Factor I/K is frequently referred to as the "compliance" of the belt, in units of strain per pound. Thus from Eq 9 it can be noted that creep is directly proportional to the product of load and compliance.
tion of the multiple-pulley drive on previous page):
Power losses Ignoring windage and hysteresis losses (the energy converted into heat by the belt during the stretch and relaxation cycles), the power relationships are Driven pulley (10) (11) The power loss is
(17)
Thus
(12)
Driving pulley
(16)
where
(18)
Belt creep—multiple pulleys Employing the same analytical approach to arrangements with three or more pulleys results in the following equations (refer also to the illustra-
of tangency and ends short of the other line of tangency. Pulley A (driver) Similar to Eq 12:
(19)
Hence
Pulley B (1st driven)
(20) (21)
Therefore and
(13) An ideal driving pulley will recover the power T2F1 and its power output will be (14) Hence, subtracting Eq 14 from Eq 13, the power loss is equal to (15) Because T1 is greater than T^ comparing Eq 15 with Eq 12 shows that the power loss at the driven pulley is slightly greater than the loss at the driver.
STEEL-TAPE DRIVE
From this it can be concluded (23) that the creep with respect to the driving pulley speed will increase as we go from pulley to pulley through the driven series of belts. Therefore it is not possible to have a reversible drive with a constant ratio between any two pulleys if there are more than two pulleys in the chain (not counting idlers). Power loss—multiple pulleys The power loss is due to friction in the areas, where the belt must slip to transmit the difference in tension. For all drivers and loads, this area of slippage begins at the unreeling line
Copyright © 2005 by The McGraw-Hill Companies
Pulley C (2nd driven)
(22)
To add the power losses of the two driven pulleys, note that TX>T2>TZ, and Vi>Vt>Vz, hence
or
Thus, the power losses of all the driven pulleys together is slightly greater than the loss at the driver. Example—steel-tape drive To show the use of the design equa-
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BELT AND ROPE PROPERTIES
TYPE
MATERIAL
COEFFICIENT OF FRICTION, n (ON CAST IRON PULLEYS)
FLAT BELT
LEATHER WOVEN COTTON WOVEN HAIR BALATA RUBBER STEEL
0.25 TO 0.2 TO 0.2 TO 0.3 TO 0.2 TO 0.15 TO
MODULUS OF ELASTICITY, PSI
WORKING STRENGTH (MAXIMUM TENSION), PSI
0.035 0.035 0.035 0.04 0.045 0.28
20,000 40,000 30,000 50,000 30,000 1 30 X 10'
300 TO 300 TO 300 TO 400 TO 400 TO 10,000
Co py rig hte dM ate ria l
V-BELT
0.35 0.3 0.3 0.4 0.3 0.25
DENSITY LB/lN.a
FABRIC SET IN RUBBER
0.25 TO 0.35
0.04
35,000
400
COTTON ROPES
STRANDED COTTON
0.2 TO 0.3
0.28D-> IB/FT D IN. = DIA
VARIABLE
200
WIRE ROPES
STRANDED STEEL WIRE
0.15 TO 0.25
1.5D2 LB/FT D IN. = DIAMETER
VARIABLE
4000
500 400 400 500 500
From G. H. Ryder
tions, assume that the three-pulley drive, at left, employs a 0.020 x 1 AAn. steel tape. To avoid overstressing the tape, the drive uses 2-in.-dia pulleys. Pulley A drives the belt system. Pulley B is coupled to an indicator with a 0.5-in.-lb load. Pulley C is coupled to a mechanism with a 5-in.-lb load. Other design specifications are: Coefficient of friction for steel tape (see table), ft = 0.2. Angle 6 for pulley A = 160 deg. Belt speed, V1 = 20 in./sec. Tension, T1, by preloading the belt = 10 Ib. Thus
This amount is sufficient for proper belt seating, yet within the lO,OOO-psi limit (from the table) for the steel belt. Calculations for the tape tensions are as follows:
This value is the maximum permissible tension at the high-tension side of the drive—the belt will slip with higher tensions. (The actual T2 value will depend on the driven loads and should be less than 17.5 Ib.) Thus the tension drop available for work is
Because R = 1 in., the maximum torque that can be transmitted is (1) (7.5) = 7.5 in,-Ib, which is greater than the 5.5 in. Ib total load requirement.
It has been shown that the design is adequate at the driver pulley. The two driven pulleys will now be examined. Pulley C—major load To determine the minimum angle of wrap at pulley C, it is convenient and conservative to ignore the tension drop across the Vi-in.-lb load. In other words, assume that
where the value for K was previously computer on page 87.
To support this contention, note that for the equation
when 6B = 0, T3ZT1 - 1. But at any positive value of 0, TJT1 > 1, or T8 > Tx. Returning to the analysis of pulley C, the maximum possible torque is 5 in.-Ib, or 5 Ib at the 1-in. radius. Hence the actual T2 tension will be
It is safe to assumt that the power losses for both driven pulleys are very nearly equal to the loss at the driver. Hence, the total power loss is approximately 0.022 in.-lb/sec. Input power = 20 in./sec x 5.5 Ib = 110 in.-lb/sec; therefore the efficiency of the tape drive is
A wrap angle of less than 115 deg may cause slippage at pulley C. Pulley B—minor load In a similar manner
This example shows why X-Y curve plotters and other instruments often use steel tapes for drives. The low creep rate resulting from the high modulus of steel permits use of a band that is not indexed to any pulley in the drive and can still indicate position repeatably.
The power loss at the driver is
Copyright © 2005 by The McGraw-Hill Companies
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M e c h a n i s m s o f
B e l t
f o r
A d j u s t i n g
T e n s i o n
D r i v e s
Sketches show devices for both manual and automatic take-up as required by wear or stretch. Some are for installations having fixed center distances; others are of the expanding center take-up types. Many units provide for adjustment of speed as well as tension.
Co py rig hte dM ate ria l
Joseph H. Gepfect
Dash pot
Lock screw
Fig. 1—Manually adjusted idler run on slack side of chain or flat belt. Useful where speed is constant, load is uniform and the tension adjustment is not critical. Can be adjusted while drive is running. Plorsepower capacity depends upon belt tension.
Driver
Spring or weight
Fig. 2—Spring or weight loaded idler run on slack side of flat belt or chain provides automatic adjustment. For constant speed but either uniform or pulsating loads. Adjustments should be made while drive is running. Capacity limited by spring or weight value.
Driver,
Locknut
Sheave or flat pulley
Fig. 5—Screw type split sheave for V-belts when tension adjustment is not critical. Best suited for installations with uniform loads. Running speed increases with take up. Drive must be stopped to make adjustments. Capacity depends directly upon value of belt tension.
Sheave or flat putty
Spring'
Fig. 6—Split sheave unit for automatic adjustment of V-belts. Tension on belt remains constant; speed increases with belt take up. Spring establishes maximum torque capacity of the drive. Hence, this can be used as a torque limiting or overload device.
Spring
Pivot
Fig. 9—Spring actuated base for automatic adjustment of uniformly loaded chain drive. With belts, it provides slipping for starting and suddenly applied torque. Can also be used to establish a safety limit for the horsepower capacity of belts.
Fig. 10—Gravity actuated pivoting motor base for uniformly loaded belts or chains, only. Same safety and slipping characteristics as that of Fig. 9. Position of motor from pivot controls the proportion of motor weight effective in producing belt tension.
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l Motor base
Fig. 3—Screw-base type unit provides normal tension control of belt or chain drive for motors. Wide range of adjustments can be made either while unit is running or stopped. With split sheaves, this device can be used to control speed as well as tension.
Fig. 4—Pivoting screw base for normal adjustment of motor drive tension. Like that of Fig. 3, this design can be adjusted either while running or stopped and will provide speed adjustment when used with split sheaves. Easier to adjust than previous design.
Thrust bearings
Driver
Thrust bearing
Sheave or fiat pulley
Beit tension screw
Fig. 7—-Another manually adjusted screw type split sheave for V-belts. However, this unit can be adjusted while the drive is running. Other characteristics similar to those of Fig. 6. Like Fig. 6, sheave spacing can be changed to maintain speed or to vary speed.
Shaft mounted gear reducer
Fig. 8—Special split sheaves for accurate tension and speed control of V-belts or chains. Applicable to parallel shafts on short center distances. Manually adjusted with belt tension screw. No change in speed with changes in tension.
Driver shaft
Weight
Adjustable torque arm
Fig. 11—Torque arm adjustment for use with shaft mounted speed reducer. Can be used as belt or chain take up for normal wear and stretch within the swing radius of reducer; or for changing speed while running when spring type split sheave is used on motor.
Copyright © 2005 by The McGraw-Hill Companies
Fig. 12—Wrapping type automatic take-up for flat and wire belts of any width. Used for maximum driving capacity. Size of weight determines tension put on belt. Maximum value should be established to protect the belt from being overloaded.
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L e a t h e r
B e l t s - H p
L o s s
a n d
S p e e d s
From 0-10,000 ft/min and 435-3450 rpm, for pulley diameters up to 30 in. Douglas C. Greenwood
secants parallel to the axes connect any four values in correct relationship. In the sample construction, a 12 in. dia pulley at 1150 rpm gives a belt velocity of about 3620 fps at which speed there is a 12% hp reduction. Consult belt manufacturer regarding suitability, efficiency and other factors in high-speed applications.
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Pulley dia , in.
Horsepower, % reduction
^m Wmorsepower ratings and correction factors for various leather belt sizes, tensions, and operating conditions are given by most engineering handbooks or manufacturers' catalogs. Such data, however, are usually not corrected for centrifugal force. This chart may be entered at any axis or pulley-speed curve. As shown,
Check with belt manufacturer for speeds in shaded areas.
Belt speed, ft /min Copyright © 2005 by The McGraw-Hill Companies
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
10
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SHAFTS & COUPLINGS Overveiw of Shafts & Coupn ilgs Critical Speeds of End Suppore td Bare Shafts Shaft Torque: Charts Fn id Equv iae lnt Seco tins Novel Ln ikage for Coupn ilg Ofset Shafts Coupn ilg of Paralel Shafts LowC -ost Meh tods of Coupn ilg Smal Da imeter Shafts Typc ial Meh tods of Coupn ilg Rotan tig Shafts I Typc ial Meh tods of Coupn ilg Rotan tig Shafts M Typc ial Desg ins of Fe lxb ie l Coupn ilgs I Typc ial Desg ins of Fe lxb ie l Coupn ilgs Il Typc ial Desg ins of Fe lxb ie l Coupn ilgs Ml Ten Unv iersal Shaft Coupn ilgs Novel Coupn ilg Shfits Shafts
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10-2 10-5 10-6 10-8 10-10 10-12 10-14 10-16 10-18 10-20 10-22 10-24 10-26
O v e r v i e w
o f
S h a f t s
&
C o u p l i n g s
Robert O . Parmley (from Mechanical Components Handbook, © 1985) •TWISTING PLANE SECURED END T (TOROUE)
NORMAL PLANE
SHAFTS
4-1
Co py rig hte dM ate ria l
A rotating bar, usually cylindrical in shape, which transmits power is called a shaft. PoweT is delivered to the shaft through the action of an outside tangential force, resulting in a torsional action set up in the shaft. The resultant torque allows the power to be distributed to other machines or to various components connected to the shaft.
SHAFT FIG. 4-1 Shaft subjected to torsional stress. Shafts which are subjected to torsional force only, or those with a minimal bending moment that can be disregarded, may use the following formula to obtain torque in inch-pounds, where horsepower P and rotational speed N in revolutions per minute are known.
Usage and Classification
Shafts and shafting may be classified according to their general usage. The following categories are presented here for discussion only and are basic in nature. Engine Shafts An engine shaft may be described as a shaft directly connected to the power delivery of a motor. Generator Shafts Generator shafts, along with engine shafts and turbine shafts, are called prime movers. There is a wide range of shaft diameters, depending on power transmission required. Turbine Shafts Also prime movers, turbine shafts have a tremendous range of diameter size. Machine Shafts General category of shafts. Variation in sizes of stock diameters ranges from ¥2 to 2V2 in (increments of 1Ae in), 2V2 to 4 in (increments of Va in), 4 to 6 in (increments of VA in). Line Shafts Line shafting is a term employed to describe long and continuous "lines of shafting," generally seen in factories, paper or steel mills, and shops where power distribution over an extended distance is required. Stock lengths of line shafting generally are 12 ft, 20 ft, and 24 ft. Jackshafts Jackshafts are used where a shaft is connected directly to a source of power from which other shafts are driven. Countershafts Countershafts are placed between a line shaft and a machine. The countershaft receives power from a line shaft and transmits it to the drive shaft. 4-2
Torsioial Stress
4-3
Twisting Moment
Twisting moment T is equal to the product of the resultant Pr of the twisting forces multiplied by its distance from the axis R. See Fig. 4-2.
4-4
(4-2)
Resisting Moment
Resisting moment Tr equals the sum of the moments of the unit shearing stresses acting along the cross section of the shaft. This moment is the force which "resists" the twisting force exerted to rotate the shaft.
KEY
AXIS CENTER
CRANK ARM
A shaft is said to be under torsional stress when one end is securely held and a twisting force acts at the opposite end. Figure 4-1 illustrates this action. Note that the only deformation in the shaft is the rotation of the cross sections with respect to each other, as shown by angle 4>.
4-5
(4-1)
SWN l G CIRCLE
FIG. 4-2 Typical crank arm forces.
KEV-
Torsion Formula for Round Shafts
Torsion formulas apply to solid or hollow circular shafts, and only when the applied force is perpendicular to the shaft's axis, if the shearing proportional limit (of the material) is not exceeded. Conditions of equilibrium, therefore, require the "twisting" moment to be opposed by an equal "resisting" moment. The following formulas may be used to solve the allowable unit shearing stress T if twisting moment T1 diameter of solid shaft D1 outside diameter of hollow shaft d, and inside diameter of hollow shaft dy are known. Solid round shafts:
A
HUB
B FLAT
F G TAPPERED PIfJ KENNEDY FIG. 4-3 Types of keys.
(4-3)
C SQUARE
D E FL.AT (SUNK) PlN (ROUND)
H ' WOODRUFF
Hollow round shafts:
cycles/s
(4-7)
(4-4)
4-6
Shear Stress
A thorough discussion of this phenomenon is beyond the scope of this book. Readers should consult the many volumes devoted to vibration theory for an in-depth technical presentation.
In terms of horsepower, for shafts used in the transmission of power, shearing stress may be calculated as follows, where P = horsepower to be transmitted, N = rotational speed in revolutions per minute, and the shaft diameters are those described previously. Maximum unit shearing stress r is in pounds per square inch. Solid round shafts:
(4-5)
Hollow round shafts: (4-6) The foregoing formulas do not consider any loads other than torsion. Weight of shaft and pulleys or belt tensions are not included. 4-7
Critical Speeds of Shafts
Shafts in rotation become very unstable at certain speeds, and damaging vibrations are likely to occur. The revolution at which this mechanical phenomenon takes place is called the "critical speed." Vibration problems may occur at a "fundamental" critical speed. The following formula is used for finding this speed for a shaft on two supports, where W1, W2, etc. = weights of rotating components; ^1,V2, etc. = respective static deflection of the weights; g = gravitational constant, 386 in/s2.
4-6
Fasteners for Torque Transmission
Keys Basically keys are wedge-like steel fasteners that are positioned in a gear, sprocket, pulley, or coupling and then secured to a shaft for the transmission of power. The key is the most effective and therefore the most common fastener used for this purpose. Figure 4-3 illustrates several standard key designs, including round and tapered pins. The saddle key (a) is hollowed to fit the shaft, without a keyway cut into the shaft. The flat key (b) is positioned on a planed surface of the shaft to give more frictional resistance. Both of these keys can transmit light loads. Square (c) and flat-sunk id) keys fit in mating keyways, half in the shaft and half into the hub. This positive holding power provides maximum torque transfer. Round (e) and tapered (f) pins are also an excellent method of keying hubs to shafts. Kennedy {g) and Woodruff (A) keys are widely used. Figure 4-4 pictures feather keys, which are used to prevent hubs from rotating on a shaft, but will permit the component part to move along the shaft's axis. Figure 4-4a shows a key which is relatively long for axial movement and is secured in position on the shaft with two flat fillister-head matching screws. Figure 4-46 is held to the hub and moves freely with the hub along the shaft's keyseat. A more in-depth presentation of keys will be found in Sec. 12, "Locking Components." Set Screws Set screws may be used for light applications. A headless screw with a hexagon socket head and a conical tip should be used. Figure 4-5 illustrates both a "good" design and a "bad" design. The set screw must be threaded into the hub and tightened on the shaft to provide a positive anchor.
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One may think of splines as a series of teeth, cut longitudinally into the external circumference of a shaft, that match or mate with a similar series of keyways cut into the hub of a mounted component. Splines are extremely effective when a "sliding" connection is necessary, such as for a PTO (power take-off) on agricultural equipment. Square or parallel-side splines are employed as multispline shaft fittings in series of 4, 6,10, or 16. Splines are especially successful when heavy torque loads and/or reversing loads are transmitted. Torque capacity (in inch-pounds) of spline fittings may be calculated by the following formula: B
in -Ib
Co py rig hte dM ate ria l
A FIG. 4-4 Feather keys.
Pins Round and taper pins were briefly discussed previously, but mention should be made of the groove, spring, spiral, and shear pins. The groove pin has one or more longitudinal grooves, known as flutes, over a portion of its length. The farther you insert this pin, the tighter it becomes. The spring or slotted tubular pin is a hollow tube with a full-length slot and tapered ends. This slot allows the pin's diameter to be reduced somewhat when the pin is inserted, thus providing easy adaptation to irregular holes. Spirally coiled pins are very similar in application to spring pins. They are fabricated from a sheet of metal wrapped twice around itself, forming a spiral effect. Shear pins, of course, are used as a weak link. They are designed to fail when a predetermined force is encountered.
where N r h L
(4-8)
= number of splines = mean radial distance from center of shaft/hub to center of spline = depth of spline = length of spline bearing surface
This gives torque based on spline side pressure of 1000 lb/in2. Involute splines are similar in design to gear teeth, but modified from the standard profile. This involute contour provides greater strength and is easier to fabricate. Figure 4-6 shows five typical involute spline shapes.
SHAFT COUPLINGS
4-9
In machine design, it often becomes necessary to fasten or join the ends of two shafts axially so that they will act as a single unit to transmit power. When this parameter is required, shaft couplings are called into use. Shaft couplings
Splines
Spline shafts are often used instead of keys to transmit power from hub to shaft or from shaft to hub. Splines may be either square or involute.
HUB SPLINE KEYWAY
SET SCREW
CONTACT SIDE
HUB
SHAFT SPLINE
GOOD DESIGN
SHAFT
BAD DESIGN
FIG. 4 - 5 U s e of set screws.
FtG. 4-6 Involute spline shapes.
BOLT CIRCLE DIAMETER
KEYWAY
HG. 4-7 Sleeve coupling.
are grouped into two general classifications: rigid (or solid) and flexible. A rigid coupling will not provide for shaft misalignment or reduce vibration or shock from one shaft to the other. However, flexible shaft couplings provide connection of misaligned shafts and can reduce shock and/or vibration to a degree.
4-10
NOTE: BOLTS NOT SHOWN
FIG. 4-9 Solid coupling.
4-11
Solid Coupling
The solid coupling shown in Fig. 4-9 is a tough, inexpensive, and positive shaft connector. When heavy torque transmission is required, a rigid coupling of this design is an excellent selection,
Sleeve Coupling
Sleeve coupling, as illustrated in Fig. 4-7, consists of a simple hollow cylinder which is slipped over the ends of two shafts fastened into place with a key positioned into mating keyways. This is the simplest rigid coupling in use today. Note that there are no projecting parts, so that it is very safe. Additionally, this coupling is inexpensive to fabricate. Figure 4-8 pictures two styles of sleeve couplings using standard set screws to anchor the coupling to each shaft end. One design is used for shafts of equal diameters. The other design connects two shafts of unequal diameters.
4-12
Clamp or Compression Coupling
The rigid coupling shown in Fig. 4-10 has evolved from the basic sleeve coupling. This clamp or compression coupling simply splits into halves, which have recesses for through bolts that secure or clamp the mating parts together, producing a compression effect on the two connecting shafts. This coupling may be used for transmission of large torques because of its positive grip from frictional contact. 4-13
Flange Coupling
Flange couplings are rigid shaft connectors, also known as solid couplings. Figure 4-11 illustrates a typical design. This rigid coupling consists of two components, which are connected to the two shafts with keys. The hub halves A
B
SET SCREWS
FIG. 4-8 Sleeve shaft coupling. FIG. 4-10 Clamp or compression coupling.
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SHAFT
BOLT-
WASHER
WASHER-
LOCKNUT
A-A
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SECTION
SECTION A-A
•BOLT CIRCLE DlA.
YOKE
FIG. 4-11 Flange coupling.
YOKE-
FIG. 4-13 Universal coupling,
are fastened together with a series of bolts arranged in an even pattern concentrically about the center of the shaft. A flange on the outside circumference of the hub provides a safety guard for the bolt heads and nuts, while adding strength to the total assembly. 4-14
Flexible Coupling
Flexible couplings connect two shafts which have some nonalignment between them. The couplings also absorb some shock and vibration which may be transmitted from one shaft to the other. There are a wide variety of flexible-coupling designs. Figure 4-12 pictures a two-part cast-iron coupling which is fastened onto the shafts by keys and set CENTER LEATHER DISK
screws. The halves have lugs, which are cast an an integral part of each hub half. The lugs fit into entry pockets in a disk made of leather plies which are stitched and cemented together. The center leather laminated disk provides flexibility in all directions. Rotation speed, either slow or fast, will not affect the efficiency of the coupling. 4-15
4-16
4-17
HUB HALF
Flexible coupling.
Multijawed Coupling
This rigid-type shaft coupling is a special design. The coupling consists of two halves, each of which has a series of mating teeth which lock together, forming a positive jawlike connection. Set screws secure the hubs onto the respective shafts. This style of coupling is strong and yet easily dismantled. See Fig, 4-14.
SET SCREW
FIG. 4-12
Universal Coupling
If two shafts are not lined up but have intersecting centerlines or axes, a positive connection can be made with a universal coupling. Figure 4-13 details a typical universal coupling. Note that the bolts are at right angles to each other. This makes possible the peculiar action of the universal coupling. Either yoke can be rotated about the axis of each bolt so that adjustment to the angle between connected shafts can be made. A good rule of thumb is not to exceed 15° of adjustment per coupling.
Spider-Type Coupling
The spider-type or Oldham coupling is a form of flexible coupling that was designed for connection of two shafts which are parallel but not in line. The two end hubs, which are connected to the two respective shafts, have grooved
SET SCREWS
PlN TYPE
P]N TYPE
T-AWA YREW SU ET SC j№, C
FIG. 4-14 Multijawed coupling.
faces which mate with the two tongues of the center disk. This configuration and slot adjustment allow for misalignment of shafts. Figure 4-15 shows an assembled spider-type coupling. 4-18
Bellows Coupling
Two styles of bellows couplings are illustrated in Fig. 4-16. These couplings are used in applications involving large amounts of shaft misalignment, usually combined with low radial loads. Maximum permissible angular misalignment varies between 5° and 10°, depending on manufacturer's recommendation. Follow manufacturer's guidelines for maximum allowable torque. Generally, these couplings are used in small, light-duty equipment. 4-19
Helical Coupling
These couplings, also, are employed to minimize the forces acting on shafts and bearings as a result of angular and/or parallel misalignment. CENTER OiSK EMD HUB
CLAMP TYPE
CLAMP TYPE FIG. 4-16 Bellows couplings.
FIG. 4-17 Helical couplings.
SHAFT
+ 30" OFFSETSHAFT SEPARATION
TYPICAL SET SCREW
SHAFT FtG. 4-18 Offset extension shaft coupling.
These couplings are used when motion must be transmitted from shaft to shaft with constant velocity and zero backlash. The helical coupling achieves these parameters by virtue of its patented design, which consists of a one-piece construction with a machined helical groove circling its exterior diameter. Removal of this coil or helical strip results in a flexible unit with considerable torsional strength. See Fig. 4-17, which pictures both the pin- and clamp-type designs. 4-20
Offset Extension Coupling
Figure 4-18 depicts an offset extension shaft coupling. This coupling is used to connect or join parallel drive shafts that are offset ±30° in any direction, with separations generally greater than 3 in. Shafts are secured to the coupling with set screws. END HUB SHAFT FIG. 4-15 Spider-type coupling.
REFERENCES Master Catalog 82. Sterling Instrument Division of Designation i™, Inc., New Hyds Park, N.Y. Levins™, Erving J.: Machine Design, Reston Publishing Co., Rest™, Va , 1978. Parmley, R 0.; Standard Handbook of Fastening andJnimng, UcUrnw-HiJl. New Yurk, 1977.
Spotts, M F.-.DesignofMackineElements, SLh «d., Prentice-Hall, Englewood Cliffs, N.J., 1978. Winston, Stanton E.: Machine Design, American Technical Society, Chicago, 19SS. Carmichael, Colin, ad.: Kent's Afwhanirnl Engineer's Handbook. 12th ed., Wiley. New York, 1958.
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C r i t i c a l E n d
S p e e d s
S u p p o r t e d
o f B a r e
S h a f t s
L. Morgan Porter
solves the equation for the critical speed of a bare steel shaft that is hinged at the bearings. For one bearing fixed and the other hinged multiply the critical speed by 1.56. For both bearings fixed, multiply the critical
speed by 2.27. The scales for critical speed and length of shaft are folded; the right hand sides, or the left hand sides, of each are used together. The chart is valid for both hollow and solid shafts. For solid shafts, D 2 = 0.
Co py rig hte dM ate ria l
THIS NOMOGRAM
^DfTHf
Shaft Length, L, in.
Critical Speed, Nc,rpm
where D1 = O D D2=ID
Example;
For Aluminum multiply values of Nc by 1.0026 For Magnesium multiply values of Ncby 0.9879
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S h a f t
T o r q u e :
C h a r t s
F i n d
E q u i v a l e n t
S e c t i o n s
An easy way to convert solid circular shafts to equivalent-strength shafts of hollow circular, elliptical, square, and rectangular sections.
Co py rig hte dM ate ria l
Dr. Biswa Nath Ghosh
1—ROUND
and
ELLIPTICAL
SHAFTS
Max shear stress, f, psi
Torque, T, fn.-lb
Example Hinds D for T^-17,300 in.~!b and max permissible shear stress = 18,000psL Example 2 finds d/ for equivalent - strength, hollow shaft of ratio do/di=/.6. Example 3 finds ds for elliptical shaft ofdm = 2.4 in. Note: For hollow shafts when d/ = D1 d0 = d/ x 1.2207. This value is specially located on the ratio scale.
Solid dio, D
Minor dio, ds, in. ond Inner dia, df, in.
Major dia, d m , in.
Ratio, do/dj
Shaft section
Location of max shear
Torque formulas: T=
Outer fiber
Outer fiber Ends of minor axis CONTINUED
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2 — S Q U A R E and RECTANGULAR
SHAFTS
Torque, T, in.-Ib
Max shear stress, f, psi
Co py rig hte dM ate ria l
Example 4 finds S for square shaff that will transmit 17,300in.-Ib forque of 18,000psi shear sfress. Example 5 finds A for reef angular shaff for ratio A/B = L 20 Square side, S, in.
Major side, A, in.
Ratio, A/B
Example 5
Shaft section
Location of max shear
Torque formulas: T=
Middle of sides
Midpoint of major sides
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N o v e l
L i n k a g e
f o r
C o u p l i n g
O f f s e t
S h a f t s
...simplifies the design of a variety of products.
Co py rig hte dM ate ria l Linkl
Position of output shaft
Link 3
Input shaft
Maximum displacement (rear view)
Input and output shafts in line Zero displacement Parallel-link connections between disks (sketch at upper left) exactly duplicate motion between input and output shafts—the basis of a new principle in coupling. Lower diagrams show three positions of links as one shaft is shifted with respect to the other shaft in the system.
Torque ratio
Link 2
An unorthodox yet remarkably simple arrangement of links and disks forms the basis of a versatile type of parallel-shaft coupling. This type of coupling—essentially three disks rotating in unison and interconnected in series by six links (drawing, left)—can adapt to wide variations in axial displacement while running under load. Changes in radial displacement do not affect the constant-velocity relationship between input and output shafts, nor do they initial radial reaction forces that might cause imbalance in the system. These features open up unusual applications in automotive, marine, machinetool, and rolling-mill machinery (drawings, facing page). How it works. The inventor of the coupling, Richard Schmidt of Schmidt Couplings, Inc., Madison, Ala., notes that a similar link arrangement has been known to some German engineers for years. But these engineers were discouraged from applying the theory because they erroneously assumed that the center disk had to be retained by its own bearing. Actually, Schmidt found, the center disk is free to assume its own center of rotation. In operation, all three disks rotate with equal velocity. The bearing-mounted connections of links to disks are equally spaced at 120 deg. on pitch circles of the same diameter. The distance between shafts can be varied steplessly between zero (when the shafts are in line) and a maximum that is twice the length of the links (drawings, left). There is no phase shift between shafts while the coupling is undulating. D
Midway position
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Total torque transmitted = constant
Link 1
Link 2
Link 3-
Angle of rotation Torque transmitted by three links in group adds up to a constant value regardless of the angle of rotation.
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Co py rig hte dM ate ria l
6-lihk couplings Drive shaft can be lowered to avoid causing hump in floor of car. Same arrangement can be applied to other applications jto bypass an object. ! \ \ \ \ \
Car differential can be mounted directly to frame, yvhile coupling transnhits drivingUorque[and permits wheels tp bounce upland do^wn. Arrangement al^o keeps wheels vetftical during sliock mbtion.
Double-universal joint
Space saving
Steering column cart be rotated around main axis for better comfort or driving position.
6-link couplings
Rolling mill needs a way to permit top roller to be adjusted vertically. Double universal joint, normally used, causes radial forces at the joints and requires more lateral space than the 6-link coupling.
Machine for pounding J ^ to induce farge-jamplitude vibration, pouplirig prevents vibrations from !passing on toitransniission and frame.
-shaft springs
Belt drive can be fdjustefc! for proper tension without need !for moving errtire base.
Inboard motor is segregated from propeller shock and vibration and can be mounted higher.
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C
o
u
p
l
i
n
g
o f
P a r a l l e l
S
h
a
f
t
s
Co py rig hte dM ate ria l
H. G. Conway
FIG. 1—A common method of coupling shafts is with two gears; for gears may be substituted chains, pulleys, friction drives and others. Major limitation is need for adequate center distance; however, an idler can be used for close centers as shown. This can be a plain pinion or an internal gear. Transmission is at constant velocity and axial freedom is present.
Fig. I
FIG. 2—Two universal joints and a short shaft can be used. Velocity transmission is constant between input and output shafts if the shafts remain parallel and if the end yokes are disposed symmetrically. Velocity of the central shaft fluctuates during rotation and at high speed and angles may cause vibration. The shaft offset may be varied but axial freedom requires a splined mounting of one shaft.
Fig. 2
FIG. 3—Crossed axis yoke coupling is a variation of the mechanism in Fig. 2. Each shaft has a yoke connected so that it can slide along the arms of a rigid cross member. Transmission is at a constant velocity but the shafts must remain parallel, although the offset may vary. There is no axial freedom. The central cross member describes a circle and is thus subjected to centrifugal loads.
Fig. 3
Fig.4
Fig. 5
FIG. 4—Another often used method is the Oldham coupling. The motion is at constant velocity, the central member describing a circle. The shaft offset may vary but the shafts must remain parallel. A small amount of axial freedom is possible. A tilting action of the central member can occur caused by the offset of the slots. This can be eliminated by enlarging the diameter and milling the slots in the same transverse plane.
FIG. 5—If the velocity does not have to be constant a pin and slot coupling can be used. Velocity transmission is irregular as the effective radius of operation is continually changing, the shafts must
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Co py rig hte dM ate ria l
The coupling of parallel shafts so that they rotate together is a common machine design problem. Illustrated are several methods where a constant 1:1 velocity ratio is possible and others where the velocity ratio may fluctuate during rotation. Some of the couplings have particular value for joining two shafts that may deflect or move relative to each other.
remain parallel unless a ball joint is used between the slot and pin. Axial freedom is possible but any change in the shaft offset will further affect the fluctuation of velocity transmission*
FIG. 6—The parallel-crank mechanism is sometimes used to drive the overhead camshaft on engines. Each shaft has at least two cranks connected by links and with full symmetry for constant velocity action and to avoid dead points. By using ball joints at the ends of the links, displacement between the crank assemblies is possible,
Fig, 6
FIG. 7—A mechanism kinematically equivalent to Fig. 6, can be made by substituting two circular and contacting pins for each link. Each shaft has a disk carrying three or more projecting pins, the sum of the radii of the pins being equal to the eccentricity of offset of the shafts. The lines of center between each pair of pins remain parallel as the coupling rotates. Pins do not need to be of equal diameter. Transmission is at constant velocity and axial freedom is possible.
Fig, 7
Fig. 8
Fig.9
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FIG. 9—An unusual development of the pin coupling is shown left. A large number of pins engage lenticular or shield shaped sections formed from segments of theoretical large pins. The axes forming the lenticular sections are struck from the pitch points of the coupling and the distance R + r is equal to the eccentricity between shaft centers. Velocity transmission is constant; axial freedom is possible but the shafts must remain parallel.
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L
o
w
-
C
o
u
p
C l
o i
s n
t g
M S
e m
t a
h l
l
o
d D
s i
o f a
m
e
t
e
r
S
h
a
f
t
s
Sixteen types of low-cost couplings, including flexible and non-flexible types. Most are for small diameter, lightly loaded shafts, but a few of them can also be adapted to heavy duty shafts. Some of them are currently available as standard commercial parts. Rubber s/eevey
Co py rig hte dM ate ria l
Hose clamp
Rubber base adhesive
Fig 1—Rubber sleeve has inside diameter smaller than shaft diameters. Using rubber-base adhesive will increase the torque capacity.
Spiff flexible
Spring
sleeve
Fig 2—Slit sleeve of rubber or other flexible material is held by hose clamps. Easy to install and remove. Absorbs vibration and shock loads.
Fig 3—Ends of spring extend through holes in shafts to form coupling. Dia of spring determined by shaft dia, wire dia determined by loads.
Sprockets
Chain
Fig 7—Jaw-type coupling is secured to shafts with straight pins. Commercially available; some have flexible insulators between jaws.
Pins,
Fig 8—Removable type coupling with insulated coupling pin. A set screw in the collar of each stamped member is used to fasten it to the shaft.
Steel sleeve
Fig 9—Sprockets mounted on each shaft are linked together with roller chain. Wide range of torque capacity. Commercially available.
Key,
Steel sleeve
Setscrew
Fig 13—Steel sleeve coupling fastened to shafts with two straight pins. Pins are staggered at 90 degree intervals to reduce the stress concentration.
Fig 14—Single key engages both shafts and metal sleeve which is attached to one shaft with setscrew. Shoulder on sleeve can be omitted to reduce costs.
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Pin
Knurled or serrated end of shaft
Co py rig hte dM ate ria l
Screw
Fig 4—Tongue - and - groove coupling made from shaft ends is used to transmit torque. Pin or set screw keeps shafts in proper alignment.
Pin
Fig 5—Screw fastens hollow shaft to inner shaft. Set screw can be used for small shafts and low torque by milling a flat on the inner shaft.
Leather or rubber disk
Fig 6—Knurled or serrated shaft is pressed into hollow shaft. Effects of misalignment must be checked to prevent overloading the bearings.
FIangedcoup/ings
Key
Key
Setscrews
Fig 10—Coupling made of two collars fastened to shafts with set screws. Pin in one collar engages hole in other. Soft spacer can be used as cushion.
Collar,
Slotted sleeve
Fig 11—Coupling is made from two flanges rivited to leather or rubber center disk. Flanges are fastened to the shafts by means of setscrews.
Fig 12—Bolted flange couplings are used on shafts from one to twelve inches in diameter. Flanges are joined by four bolts and are keyed to shafts.
Metal ends*
Collar
Setscrew
Rubber hose
Fig 15—Screwing split collars on tapered threads of slotted sleeve tightens coupling. For light loads and small shafts, sleeve can be made of plastic material.
Fig 16—One-piece flexible coupling has rubber hose with metallic ends that are fastened to shafts with set screws. Commercially available in several sizes and lengths.
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T y p i c a l
M e t h o d s
C o u p l i n g
o f
R o t a t i n g
S h a f t s
I
Co py rig hte dM ate ria l
Methods of coupling rotating shafts vary from simple bolted flange constructions to complex spring and synthetic rubber mechanisms. Some types incorporating chain, belts, splines, bands, and rollers are described and illustrated below.
Each set of splines in mesh Gasket between housing Steel grid transmits Floating sleeve, carrying around entire circumferenc flanges retains lubricant •power and absorbs generated internal splines A ssembly revolves as one shock and vibration at each end. The splines of the sleeve permanently en- unit L ateral and angular play allowedbetween spline gage the splines ofeach hub, faces Flanges of hous/ng Hubs are pressed on and keyed to each bo/tedtogether shaft. Each hub carries generated splines, SleeveJack holes to cut at maximum distance from shaft end facilitate separation of center flanges Misalignment ofcon- OH fillerplug nected shafts is compensated by sleeve assuming neutral position between FIG.1 shafthubs
Clearance between casing and hub to allow Sleeve bearings lateral float for carriedon bearing each shaft 'Boitheads and rings. Rings located nuts in flanges on transverse center Tapered grooves for Load is earned counterbored line of hub spline faces Neoprene seal rings grid provide bearing by oil film as safetyprecaution retain lubricant surface. 6rid bears in grooves in proporHub jack holes ViI levels. Coupling is fft ted when standing. Oil film between splines tion to load to facilitate Filler hole for lubricant installation or In operation centrifu- eliminates metal-to-metal The FaIk Corp, removal ofhubsgal force distributes contact oil to immerse splines
Hubs keyed for shafts
FIG. 2
Oil hole with safety screwplug
Bar+Ieff- Hayward Div., (Coppers Co., Inc.
-Floating housing shelf cut with internal gears Tapered bores do not af each end run completely through
Double - tapered jaws held by keyseats in end of hub
hubs'
Bottholes counterbored as safety precaution
Generated spherical gears on hubs.
Shaft
Hubs spiined for shafts Casket between flanges to ensure o/l tight sect! FIG. 3
Oil seal of flexible composition material Clearance space between hubs to allow for endplay
Flanged hubs
1
Barcus Engineering Co.,Inc-
Jaws machinedor? inner surface to radius less than shaft. Shaftgripped jby Jaws when flanges are drawn together by bolts
BoItS draw flanged hubs together
Copyright © 2005 by The McGraw-Hill Companies
FIG. 4
W. H Nicholson and Co
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Steelrims,one ofwhich is of smaller diameter hian the other
Co py rig hte dM ate ria l
Rims mounted on flanges
,—Unless leather bett laced through alternate rim slots
Rims-
FIG. 5
Removable access plate to springs
Casingprovided with tugs that fit loosely in the twinarms of the spider and bear against spring plugs
Casing and spider keyed to shaft
Axial slots on each rim
flanges-keyed to shaft
Helical springs in constant compression
Spider
Shaft-
Clearance between ends ofspringpk/gs less than maximum deflection of spring Sudden overload am not break springs
FIG. 6
Smooth exterior for safety
Helical springs
Cy/indricat sfeeve with eccentric chambers on inside
Smooth exterior fbr safety
Turning coupling forces rollers up inclinedsides ofeccenhric chamber fo lock coupling to shaft
Case-hardened plugs fitted into pockets between twin-arms of spider
Side c/earance provided between chain ana/teeth for accomodahon of angt//ar displacement Rotter chain over teeth on between shafts hub flanges. Alt rollers /n contact with teeth fyreqvat distribution of transmitted toad Teeth cut on flanges ofhubs
FIG. 7 FIG. 8
With rotters located in fargest port ofeccentric chamber coupling can be slipped over end of shaft
Two steel rotters he/atparatfet by tight wire frame
Copyright © 2005 by The McGraw-Hill Companies
Chainprovided w/th masterfink fbrremova/
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Hubs keyed to shafts
T y p i c a l
M e t h o d s
C o u p l i n g
o f
R o t a t i n g
S h a f t s
I l
Shafts couplings that utilize internal and external gears, balls, pins and non-metallic parts to transmit torque are shown herewith. T
Mefa/ facing p/ateS riveted to flexible disk prevent excessive we&r-
flange
F/exibfe disk of vu/c&nized rubbered fabric
E/ongoifed ho/es receive boss from mating -flange
Co py rig hte dM ate ria l
Metaf housing over neoprene biscuits
F/ange hubs keyed to Shafts
Bosses on metal flanges potss through holes in flexible disk and enter elongated holes. in ma Hng flange
Neoprene center designed for uniform stress, line&r deflection atnd absorption of vibration Shaft keyed to flange-\
Boston Gear Work, Inc.
FIG.2
Setsere ws secure hubs to shaft
Keyed
Shaft
Metallic screen core
T
FIG.1
Compensating member provides connection between hub and oofe^ s/eeve F/anged hub keyed to shaft
Morse Chain Co
F/anged outers/eeve bo/ted a/ire ct/y to f/anged hub
Geared
hub keyed to shaft
Flexible, oil-resistant packing ret&rns oil inside the coupling and excludes alirf, grit and moisture FIG. A-
Boston Gear Works, Inc.
Long gear teeth in s/eeve prevent hub from dise ngaging
Wide face of internal gear teeth per/nits full end float without disengagement
Generated external/ and in ternaf gear teeth
FiG.5
flange
Outer fabric r/'ng impregnated with neoprene, provides support for center section
Tapped ho/es fcrcf/ftate assembly and dfs~ assembly
large number of teeth produce very large bearing surface
Two tapped holes In each hub facififcrte assembly andremoval Gasket prevents oi/ leakage
Ctearance between s/eeve and hub permits free end ffocxt
•Loord cushioned by oil f/'f/n between the gear teeth
Solid me tot I under gear teeth gives added s trength an of durabifity Ftexibfe, oi/ resistant packing retains oi/ inside the coup/ing and excludes dirt, grit an d mois tare
Generated external and intern or I gear teeth
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Of/ chamber
Machined bands on each hub fact•"/
Safety flange with countersunk holes for fitted bolts and self-locking nuts
Fcarrel-Birmingham Co., Inc.
Sphericot/ contour of hub teeth permits free s/iding and rocking motion
Two tapped holes in each half of sleeve 'Off-supply replenished facilitate assembly through either of two plugged holes and removal FIG.5
Parrel Bfrminghoim Co., Inc.
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vuicanized plates
Outer fabric ring impregnated with neoprene, provides support for center section
Trunnion pins fitted into outer diameter ofhub and welded
M eta/Uc screen core
Co py rig hte dM ate ria l
Rubber to steel
Plates bolted to ffamges—
-Neoprene center designed for uniform stress
Shaft
Keywo/y
Hange keyed to shaft
Boithecfds recessed cvs safety precaution*
FIG.6
Hubs secured to shafts by keys and sets crews
Non-mefaiHc insert between jaws of coupling absorbs vibration and shocks
Two-piece housing clamps cvround neoprene biscuits. Face of housing attaches to standard ffange
FIG.7
Morse Chain Co.
Bali bearing insert permits unrestricted endp/ay
FIG.8
Neoprene /biscuit pressed over trunnion blocks
Hubs secured to shafts by keys and setscrews
Bosfon Gear Works, Inc.
FlexiSie famine/fed pin units compensate for misalignment of connected shafts. One end held by spring retaining ring, other end moves laterally in bushing
Spring retaining ring holds flexible pin units in flange
Steel laminations swivel on cross pins in siot of keeper
Fiange hubs secured to shaft wifh set screws and keys "
FIG. 9
Bos+on Gear Works^ Inc.
Nc lubrication is required on this coup/ing Sails contained in pockets in f/angre
Projection on retaining cover holds balls in p roper p os ition
Hubs keyed for shcyfts
Forcep /ate retains balls
Cross pin
Wax-impregnated, bronze bushings FIG. IO
se/t
lubricating
Power mitted rubber
Sm at/holes inflctnge to aid in removing bath
transby Six bar Hs
John Watdron Corp.
Copyright © 2005 by The McGraw-Hill Companies
FIG.Il
Crocker-Wheeler DiV, Joshua Henoiy Iron Works
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T y p i c a l
D e s i g n s
o f
F l e x i b l e
C o u p l i n g s
I
Cyril Donaldson
Snafi
Hose damps
Bolt
Shaft
Co py rig hte dM ate ria l
Rubber hose F I G l Washer
Rubber hose Washer
Shaft-
FIG.2
Hole
Shaft
Setscrews
Spring
HoZe1
FIG. 3
Shaft-
Couptinq
Strandedcabte
Shaft Coupfing FIG 4 Hub
Shaft
Hub
•Spring
Cover
Fig. 1—A rubber hose clamped to two shafts. For applications where the torque is low and slippage unimportant. It is easily assembled and disconnected without disturbing either machine element. Adaptable to changes in longitudinal distance between machines. This coupling absorbs shocks, is not damaged by overloads, does not set up end thrusts, requires no lubrication and compensates for both angular and offset misalignment. Fig. 2—Similar to Fig. 1, but positive drive is assured by bolting hose to shafts. Has same advantages as type in Fig. 1, except there is no overload protection other than the rupture of the hose. Fig. 3—The use of a coiled spring fastened to shafts gives the same action as a hose. Has excellent shock absorbing qualities, but torsional vibrations are possible. Will allow end play in shafts, but sets up end thrust in so doing. Other advantages are same as in types shown in Figs. 1 and 2. Compensates for misalignment in any direction. Fig. 4—A simple and effective coupling for low torques and unidirectional rotation. Stranded cable provides a positive drive with desirable elasticity. Inertia of rotating parts is low. Easily assembled and disconnected without disturbing either shaft. Cable can be encased and length extended to allow for right angle bends such as used on dental drills and speedometer drives. Ends of cable are soldered or bound with wire to prevent unraveling. Fig. 5—A type of FaIk coupling that operates on the same principle as design shown in Fig. 6, but has a single flat spring in place of a series of coiled springs. High degree of flexibility obtained by use of tapered slots in hubs. Smooth operation, is maintained by inclosing the working parts and packing with grease. Fig. 6—Two flanges and a series of coiled springs give a high degree of flexibility. Used only where the shafts have no free end play. Needs no lubrication, absorbs shocks and provides protec-
FIG.5
Coiled springs
Rubber tubing
Bolt
Flange
Rubber bushings, Pin
-Shaff
Washer
Flange Keys
Keys
Shaft
Shaft Shaft
Flange
Flange Flange Flange
FIG.8
FIG,7
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Co py rig hte dM ate ria l
tion against overloads, but will set up torsional vibrations. Springs can be of round or square wire with varying sizes and pitches to allow for any degree of flexibility. Fig. 7—Is similar to Fig. 6, except that rubber tubing, reinforced by bolts, is used instead of coiled springs. Is of sturdier construction but more limited in flexibility. Has no.overload protection other than shearing of the bolts. Good anti-vibration properties if thick rubber tubing is used. Can absorb minor shocks. Connection can be quickly disassembled. Fig. 8—A series of pins engage rubber bushings cemented into flange. Coupling is easy to install. Flanges being accurately machined and of identical size makes accurate lining-up with spirit level possible. Will allow minor end play in shafts, and provides a positive drive with good flexibility in all direction. Fig. 9—A Foote Gear Works flexible coupling which has shear pins in a separate set of bushings to provide overload protection. Construction of studs, rubber bushings and self-lubricating bronze bearings is in principle similar to that shown in Fig. 10. Replaceable shear pins are made of softer material than the shear pin bushings. Fig. 10—A design made by the Ajax Flexible Coupling Company. Studs are firmly anchored with nuts and lock washers and bear in self-lubricating bronze bushings spaced alternately in both flanges. Thick rubber bushings cemented in flanges are forced over the bronze bushings. Life of coupling said to be considerably increased because of self-lubricated bushings. Fig. 11—Another Foote Gear Works coupling. Flexibility is obtained by solid conicallyTshaped pins of metal or fiber. This type of pin is said to provide a positive drive of sturdy construction with flexibility in all directions. Fig. 12—In this Smith & Serrell coupling a high degree of flexibility is obtained by laminated pins built-up of tempered spring steel leaves. Spring leaves secured to holder by keeper pin. Phosphor bronze bearing strips are welded to outer spring leaves and bear in rectangular holes of hardened steel bushings fastened in flange. Pins are free to slide endwise in one flange, but are locked in the other flange by a spring retaining ring. This type is used for severe duty in both marine and land service.
Rubber bushing ff/vsze bushing
Stud-
FlG. 10
K?y
Shaft
Flange
ShaftFlange FIG. 11
Flange
Spring retaining rina t?eef>er pin
Flange
fhstbf flat Springs
Rubber bushing Bronze bushing Stud
Fl 6.12
Shaft
Section Through Center
Shear pin Fl G. 9
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Bushing
T y p i c a l
D e s i g n s
o f
F l e x i b l e
C o u p l i n g s
I l
Cyril Donaldson Buffers/of.
Steel pins
Co py rig hte dM ate ria l
Fl G. 13
Rubber, leather or fiber disk
Fl G. 14
Flexible disks
FIG.15
Fig. 13—In this Brown Engineering Company coupling flexibility is increased by addition of buffer-slots in the laminated leather. These slots also aid in the absorption of shock loads and torsional vibration. Under parallel misalignment or shock loads, buffer slots will close over their entire width, but under angular misalignment buffer slots will close only on one side. Fig. 14—Flexibility is provided by resilience of a rubber, leather, or fiber disk in this W. A. Jones Foundry & Machine Company coupling. Degree of flexibility is limited to clearance between pins and holes in the disk plus the resilience of the disk. Has good shock absorbing properties, allows for end play and needs no lubrication. Fig. 15—A coupling made by Aldrich Pump Company, similar to Fig. 14, except bolts are used instead of pins. This coupling permits only slight endwise movement of the shaft and allows machines to be temporarily disconnected without disturbing the flanges. Driving and driven members are flanged for protection against projecting bolts. Fig. 16—Laminated metal disks are used in this coupling made by Thomas Flexible Coupling Company. The disks are bolted to each flange and connected to each other by means of pins supported by a steel center disk. The spring action of the center ring allows torsional flexibility and the two side rings compensate for angular and offset misalignment. This type of coupling provides a positive drive in either direction without setting up backlash. No lubrication is required. Fig. 17—A design made by Palmer-Bee Company for heavy torques. Each flange carries two studs upon which are mounted square metal blocks. The blocks slide in the slots of the center metal disk.
Laminated metal disks
A
FIG.17
Metal block
Metal disk FIG.16 Center disk Copyright © 2005 by The McGraw-Hill Companies
A
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Section A-A
Rivet members
Co py rig hte dM ate ria l
Fig. 18—In this Charles Bond Company coupling a leather disk floats between two identical flanges. Drive is through four laminated leather lugs cemented and riveted to the leather disk. Compensates for misalignment in all directions and sets up no end thrusts. The flanges are made of cast iron and the driving lug slots are cored. Fig. 19—The principle of the T. B. Wood & Sons Company coupling is the same as Fig. 18, but the driving lugs are cast integrally with the metal flanges. The laminated leather disk is punched out to accommodate the metal driving lugs of each flange. This coupling has flexibility in all directions and does not require lubrication. Fig. 20—Another design made by Charles Bond Company, The flanges have square recesses into which a built-up leather cube fits. Endwise movement is prevented by through bolts set at right angles. The coupling operates quietly and is used where low torque loads are to be transmitted. Diecastings can be used for the flanges. Fig. 21—Similar to Fig. 20, being quiet in operation and used for low torques. This is also a design of Charles Bond Company. The floating member is made of laminated leather and is shaped like a cross. The ends of the intermediate member engage the two cored slots of each flange. The coupling will withstand a limited amount of end play. Fig. 22—Pins mounted in flanges are connected by leather, canvas, or rubber bands. Coupling is used for temporary connections where large torques are transmitted, such as the driving of dynamometers by test engines. Allows for a large amount of flexibility in all directions, absorbs shocks but requires frequent inspection. Machines can be quickly disconnected, especially when belt fasteners are used on the bands. Driven member lags behind driver when under load. Fig. 2.3—This Bruce-Macbeth Engine Company coupling is similar to that of Fig. 22, except that six endless wire cable links are used, made of plow-steel wire rope. The links engage small metal spools mounted on eccentric bushings. By turning these bushings the links are adjusted to the proper tension. The load is transmitted from one flange to the other by direct pull on the cable links. This type of coupling is used for severe service.
Cast iron hud
Leather disk
FI G.I 8
A
Leather disk
A
FIG.19
Section (A-A
A
A
Flange
Leather cube
S/ots
Leather cross
FIG.23
Cable /ink-
Section A~A
FIG.20
FIG.22 Band
\CabIeIinks
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Band
FIG.2I
T y p i c a l
D e s i g n s
o f
F l e x i b l e
C o u p l i n g s
I I I
Cyril Donaldson
Co py rig hte dM ate ria l
Leather belt Flange rib
HG.24
Pins
Endless ropes Pins
Flange
Fig. 24—This Webster Manufacturing Company coupling uses a single endless leather belt instead of a series of bands, as in Fig. 22. The belt is looped over alternate pins in both flanges. Has good shock resisting properties because of belt stretch and the tendency of the pins to settle back into the loops of the belt.
ne.25 Flange
Leather links
Fig. 25—This coupling made by the Weller Manufacturing Company is similar to the design in Fig. 24, but instead of a leather belt uses hemp rope, made endless by splicing. The action under load is the same as in the endless belt type.
Fig. 26—This Bruce-Macbeth design uses leather links instead of endless wire cables, as shown in Fig. 23. The load is transmitted from one flange to the other by direct pull of the links, which at the same time allows for the proper flexibility. Intended for permanent installations requiring a minimum of supervision.
Fig. 27—The Oldhani form of coupling made by W. A. Jones Foundry and Machine Company is of the two-jaw type with a metal disk. Is used for transmitting heavy loads at low speed.
FIG. 26
Leather link
Fig. 28—The Charles Bond Company star coupling is similar to the cross type shown in Fig. 21, The star-shaped floating member is made of laminated leather. Has three jaws in each flange. Torque capacity is thus increased over the two-jaw or cross type. Coupling takes care of limited end play.
Fig. 29—Combination rubber and canvas disk is bolted to two metal spiders. Extensively used for low torques where compensation for only slight angular misalignment is required. Is quiet in operation and needs no lubrication or other attention. Offset misalignment shortens disk life.
FIG. 27
Flexible disk Plain wots her
Floating disk
Leather s far
FlG. 28
FI6.29
Copyright © 2005 by The McGraw-Hill Companies
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Rubberized fabric cfisks
Co py rig hte dM ate ria l
Fig. 30—A metal block as a floating center is used in this American Flexible Coupling Company design. Quiet operation is secured by facing the block with removable fiber strips and packing the center with grease. The coupling sets up no end thrusts, is easy to assemble and does not depend on flexible material for the driving action. Can be built in small sizes by using hardwood block without facings, for the floating member. Fig. 31—This Westinghouse Nuttall Company coupling is an all-metal type having excellent torsional flexibility. The eight compression springs compensate for angular and offset misalignment. Allows for some free endwise float of the shafts. Will transmit high torques in either direction. No lubrication is needed.
FI6.32
Center spider
Spiders A
Fig. 32—Similar to Fig. 29, but will withstand offset misalignment by addition of the extra disk. In this instance the center spider is free to float. By use of two rubber-canvas disks, as shown, coupling will withstand a considerable angular misalignment.
Spiders
Fig. 33—In this Smith & Serrell coupling a flexible cross made of laminated steel strips floats between two spiders. The laminated spokes, retained by four segmental shoes, engage lugs integral with the flanges. Coupling is intended for the transmission of light loads only. Fig. 34—This coupling made by Brown Engineering Company is useful for improvising connections between apparatus in laboratories and similar temporary installations. Compensates for misalignment in all directions. Will absorb varying- degrees of torsional shocks by changing the size of the springs. Springs are retained by threaded pins engaging the coils. Overload protection is possible by the slippage or breakage of replacable springs.
Fig. 35—In another design by Brown Engineering Company, a series of laminated spokes transmit power between the two flanges without setting up end thrusts. This type allows free end play. Among other advantages are absorption of torsional shocks, has no exposed moving parts, and is well balanced at all speeds. Wearing parts are replacable and working parts are protected from dust.
FI6.33
A
Spring reicn'tning pin Bell
FIG.34
Coiled springs
FIG.31
Springs
FI6.30
Bearingf strips Section X-X
Copyright © 2005 by The McGraw-Hill Companies
Sieelsirips
Laminated spokes FI6.35
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Sec+ion A-A Reiotininof pin
Co py rig hte dM ate ria l
Hooke's Joints
Slotted shaft end
The commonest form of a universal coupling is a Hooke's joint It can transmit torque efficiently up to a maximum shaft alignment angle of about 36°. At slow speeds, on hand-operated mechanisms, the permissible angle can reach 45°. The simplest arrangement for a Hooke's joint is two forked shaft-ends coupled by a cross-shaped piece. There are many variations and a few of them are included here.
36° max
Top view
Fig. 4 A pinned-sleeve shaft-coupling is fastened to one shaft that engages the forked, spherical end on the other shaft to provide a joint which also allows for axial shaft movement. In this example, however, the angle between shafts must be small. Also, the joint is only suitable for low torques.
Crosspiece
Constant-Vefocity Couplings
Fig. 1 The Hooke's joint can transmit heavy loads. Anti-friction bearings are a refinement often used.
The disadvantages of a single Hooke's joint is that the velocity of the driven shaft varies. Its maximum velocity can be found by multiplying driving-shaft speed by the secant of the shaft angle; for minimum speed, multiply by the cosine. An example of speed variation: a driving shaft rotates at 100 rpm; the angle between the shafts is 20°. The minimum output is 100 x 0.9397, which equals 93.9 rpm; the maximum output is 1.0642 x 100, or 106.4 rpm. Thus, the difference is 12.43 rpm. When output speed is high, output torque is low, and vice versa. This is an objectionable feature in some mechanisms. However, two universal joints connected by an intermediate shaft solve this speed-torque objection.
Fig. 2 A pinned sphere shaft coupling replaces a cross-piece. The result is a more compact joint.
A
A
Section A-A
Fig. 3 A grooved-sphere joint is a modification of a pinned sphere. Torques on fastening sleeves are bent over the sphere on the assembly. Greater sliding contact of the torques in grooves makes simple lubrication essential at high torques and alignment angles.
Fig. 5 A constant-velocity joint is made by coupling two Hooke's joints. They must have equal input and output angles to work correctly. Also, the forks must be assembled so that they will always be in the same plane. The shaft-alignment angle can be double that for a single joint.
Source: Mechanisms and Mechanical Devices Sourcebook, 3E, by Chironis & Sclater, © 2001 McGraw-Hill Copyright © 2005 by The McGraw-Hill Companies
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grammatically in Fig. 7A. It has two joints dose-coupled with a sliding member between them. The exploded view (Fig. 7B) shows these members, There are other designs for heavy-duty universal couplings; one, known as the Rzeppa, consists of a cage that keeps six balls in the homokinetic plane at all times. Another constant-velocity joint, the Bendix-Weiss, also incorporates balls.
Co py rig hte dM ate ria l
This single constant-velocity coupling is based on the principle (Fig. 6) that the contact point of the two members must always lie on the homokinetic plane. Their rotation speed will then always be equal because the radius to the contact point of each member will always be equal. Such simple couplings are idea! for toys, instruments, and other light-duty mechanisms. For heavy duty, such as the front-wheel drives of military vehicles, a more complex coupling is shown dia-
Forked shafts
Protective casing Slotted joints
Homokinetic plane
Spigot joint
Radius
A
Shaft with fork Slotted joint
Radius
Spigot joint
B
Fig. 6
Flat
Fig. 7
Springs
Sliding rods
Triple-strand spring
Fig. 8 This flexible shaft permits any shaft angle. These shafts, if long, should be supported to prevent backlash and coiling. Sliding fit
Fig. 9 This pump-type coupling has the reciprocating action of sliding rods that can drive pistons in cylinders.
Swivels
Fig. 10 This light-duty coupling is ideal for many simple, low-cost mechanisms. The sliding swivei-rod must be kept well lubricated at ail times.
Copyright © 2005 by The McGraw-Hill Companies
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N o v e l
C o u p l i n g
S h i f t s
Gearshift
Clutch
Schmidt coupling
S h a f t s
Internal gear wheel
Internal gear housing External housing
Input shaft,
Co py rig hte dM ate ria l
Output shaft
'Schmidt coupling
Gear wheels
Clutch
Gearshift
Para I IeIg ram-type coupling (above) brings new versatility to gear-transmission design (left) by permitting both input and output to clutch in directly to any of six power gears.
Schmidt Coupling, Inc., Madison, AL
N o v e l to
C o u p l i n g
simplify
Shifts
Shafts:
t r a n s m i s s i o n
A unique disk-and-link coupling that can handle large axial displacement between shafts, while the shafts are running under load, is opening up new approaches to transmission design.
The coupling (drawing, upper right) maintains a constant transmission ratio between input and output shafts while the shafts undergo axial shifts in their relative positions. This permits gear-andbelt transmissions to be designed that need fewer gears and pulleys.
d e s i g n
Half as many gears. In the internal-gear transmission above, a Schmidt coupling on the input side permits the input to be "plugged-in" directly to any one of six gears, all of which are in mesh with the internal gear wheel. On the output side, after the power flows through the gear wheel, a second Schmidt coupling permits a direct power takeoff from any of the same six gears. Thus, any one of 6 x 6 minus 5 or 31 different speed ratios can be selected while the unit is running. A more orthodox design would require almost twice as many gears.
Axial thrust bearing
Gear housing
Powerful pump. In the wormtype pump (bottom left), as the input shaft rotates clockwise, the worm rotor is forced to roll around the inside of the gear housing, which has a helical groove running from end to end. Thus, the rotor centerline will rotate counterclockwise to produce a powerful pumping action for moving heavy media. In the belt drive (bottom right), the Schmidt coupling permits the belt to be shifted to a different bottom pulley while remaining on the same top pulley. Normally, because of the constant belt length, the top pulley would have to be shifted, too, to provide a choice of only three output speeds. With the new arrangement, nine different output speeds can be obtained. D
Pulleys
Housing
Worm rotor
Input shaft (stationary)
Stationary output shaft
Shiftable pulleys and drive shaft
Belt
Schmidt coupling
Schmidt coupling
Eccentric displacement of rotor shaft Gear shift
Coupling allows helical-shape rotor to wiggle for pumping purposes.
Copyright © 2005 by The McGraw-Hill Companies
Stationary input shaft
Coupling takes up slack when bottom shifts.
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
11
Co py rig hte dM ate ria l
THREADED COMPONENTS
Getn ig the Most from Screws 20 Dynamci Appc ilato ins for Screw Threads 16 Ways to Ag iln Sheets and Pa ltes wtih One Screw Varo ius Meh tods of Lockn ig Threaded Members How to Provd ie for Backalsh in Threaded Parts 7 Speca il Screw Arangemens t Wod rl of Sefl-Lockn ig Screws
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11-2 11-4 11-8 11-10 11-12 11-14 11-16
G e t t i n g
t h e
M o s t
f r o m
S c r e w s
Special jobs often call for special screw arrangements; here are some examples of how this busy fastener can perform. Federico Strasser
Co py rig hte dM ate ria l
Tapped head
Keyh
T A PE DH E A DL E T SE X T E N O S N IS B EA D D E D . Buttr Portia! threadsthrea Slotte termi end KEY-TYPE HEAD PROVIDES QUICK-RELEASE FEATURE.
o () Major d Mfn Grooved Tapered bushing • Slit nutslit* a () b () S U A EwH O E fterradeg ilhthm s u tQ ite sR e llL o fro h d o e
PARTIAL THREADS ASSEMBLE FAST, DON'T WORK LOOSE.
BUTTRESS THREADS PREVENT (a) radial forces from opening slotted ends; otherwise (b) a reinforcing sleeve is needed.
SLtT NUT (a) and tapered bushing (also slit) (b) allows backlash-free adjustment.
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l Coupling so/id rods
(a)
(t>)
TAPERED SCREWS ASSEMBLE AND RELEASE FAST, BUT WORK LOOSE EASILY. Coarse thread
Xtpi
Knob
Reinforcing sleeve
Fine thread
(a)
Y tpi.
(b)
Cb)
DIFFERENTIAL THREADS PROVIDE (a) extra tight fastening or (b) extra small relative movement, 8, per revolution of knob.
Adjusting screw
Wire hook
WIRE HOOK provides single-thread grip for low-cost device.
Copyright © 2005 by The McGraw-Hill Companies
Right-hand lead
Left-hand lead
DOUBLE SCREW for wire guide or follower always leads wire to center.
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2 0
D y n a m i c
S c r e w
A p p l i c a t i o n s
f o r
T h r e a d s
Have you forgotten how simply, and economically, screw threads can be made into dynamic members of a linkage? Here are some memory-joggers, plus suggestions for simplified nuts, threads and nut guides.
Co py rig hte dM ate ria l
Kurt Rabe
Here are the basic motion transformations possible with screw threads (Fig 1): • transform rotation into linear motion or reverse (A), • transform helical motion into linear motion or reverse (B), • transform rotation into helical motion or reverse (C). Of course the screw thread may be combined with other components: in a 4-bar linkage (Fig 2), or with multiple screw elements for force or motion amplification.
Y o u need a threaded shaft, a nut . . . plus some way for one of these members to rotate without translating and the other to translate without rotating. That's all. Yet these simple components can do practically all of the adjusting, setting, or locking used in design. Most such applications have low-precision requirements. That's why the thread may be a coiled wire or a twisted strip; the nut may be a notched ear on a shaft or a slotted disk. Standard screws and nuts right off your supply shelves can often serve at very low cost.
A
6
1 MOTION TRANSFORMATIONS of a screw thread include: rotation to translation (A), helical to translation (B), rotation to helical (C). Any of
A R e v i e w of S c r e w - T h r e a d
C
these is reversible if the thread is not self-locking (see screw-thread mathematics on following page—thread is reversible when efficiency is over 50%).
2 STANDARD 4-BAR LINKAGE has
screw thread substituted for slider. Output is helical rather than linear.
Mathematics
friction angle, tan a = / mean radius of thread = i (root radius + outside radius), in inches lead, thread advance in one revolution, in. lead angle, tan b = 1/2TT, deg friction coefficient equivalent driving force at radius r from screw axis, Ib axial load, Ib efficiency half angle between thread faces, deg
(motion opposed "to L)
(motion assisted by L)
VTHREADS:
(motion Qp posed to L)
SQUARE THREADS:
(motion assisted by L) Where upper signs are for motion opposed in direction to L. Screw is self-locking when b ^ a.
For more detailed analysis of screw-thread friction forces, see Marks Mechanical Engineers' Handbook, McGraw-Hill Book Co.
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l
Rotation to Translation
3 TWO-DIRECTIONAL LAMP ADJUSTMENT with screwdriver to move lamp up and down. Knob adjust (right) rotates lamp about pivot.
Output gear
4 KNIFE-EDGE BEARING is raised or lowered by screw-driven wedge. Two additional screws locate the knife edgQ laterally and lock it.
Clockwork housing
Ratchet
Motor drive
Switch
5 SlDE-BY-SIDE ARRANGEMENT of tandem screw threads gives parallel rise in this height adjustment for projector.
6 AUTOMATIC CLOCKWORK is kept wound tight by electric motor turned on and off by screw thread and nut. Note motor drive must be self-locking or it will permit clock to unwind as soon as switch turns off.
Copyright © 2005 by The McGraw-Hill Companies
Pressure
7 VALVE STEM has two oppositely moving valve cones. When opening, the upper cone moves up first, until it contacts its stop. Further turning of the valve wheel forces the lower cone out of its seat. The spring is wound up at the same time. When the ratchet is released, spring pulls both cones into their seats.
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Rotation
Self-Locking
Co py rig hte dM ate ria l
Translation to
Feeler
8 A M ETAL ST RIP or square rod may be twisted to make a long-lead thread, ideal for transforming linear into rotary motion. Here a pushbutton mechanism winds a camera. Note that the number of turns or dwell of output gear is easily altered by changing (or even reversing) twist of the strip.
9 FEELER GAGE has its motion amplified through a double linkage and then transformed to rotation for dial indication.
11 HAIRLINE ADJUSTMENT for a telescope, with two alternative methods of drive and spring return.
Bushing
10 THE FAMILIAR flying propellertoy is operated by pushing the bushing straight up and off the thread.
Copyright © 2005 by The McGraw-Hill Companies
12 SCREW AND NUT provide self-locking drive for a complex linkage.
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Double
Threading
14 D I F F E R E NTIAL
Co py rig hte dM ate ria l
SCREWS can be made in dozens of forms. Here are two methods: above, two opposite-hand threads on a single shaft; below, same hand threads on independent shafts.
13 DOUBLE-THREADED SCREWS/ when used as differentials, provide very fine adjustment for precision equipment at relatively low cost
1 5 OPPOSITE-HAND THREADS make a highspeed centering clamp out of two moving nuts.
Synchronous motor drive
1 6 MEASURING TABLE rises very slowly for many turns of the input bevel gear. If the two threads are 1^—12 and %—16, in the finethread series, table will rise approximately 0.004 in. per input-gear revolution.
1 7 LATHE TURNING TOOL in drill rod is adjusted by differential screw. A special doublepin wrench turns the intermediate nut, advancing the nut and retracting the threaded tool \sir raultaneously. Tool is then clamped by setscrew.
19 (left) A WIRE FORK is the nut in this simple tube-and screw design,
Follower-motor drive
2 0 (below) A MECHANICAL PENCIL includes a spring as the screw thread and a notched ear or a bent wire as the nut.
Slide adjusts follower-motor speed
Two variants of nut
1 8 A N Y VARIABLE-SPEED MOTOR can be
made to follow a small synchronous motor by connecting them to the two shafts of this differential screw. Differences in number of revolutions between the two motors appear as motion of the traveling nut and slide so an electrical speed compensation is made.
EDITOR'S NOTE: For other solutions to adjusting, setting, and locking problems in translating motion, see: 10 Ways to Employ Screw Mechanisms, May 26 '58, p 80. Shows applications in terms of three basic components—actuating member, threaded device, and sliding device. 5 Cardan-gear Mechanisms. Sep 28 '59, p 66. Gearing arrangements that convert rotation into straight-line motion. 5 Linkages for Straight-line Motion, Oct 12 J59, p 86. Linkages that convert rotation into straight-line motion.
Copyright © 2005 by The McGraw-Hill Companies
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1 6
W a y s
w i t h
t o
O n e
A l i g n
S h e e t s
a n d
P l a t e s
S c r e w
Federico Strasser
Two
Flat
Parts
Co py rig hte dM ate ria l
Dowel
Aligning tube
Retained stag
1 Dowels . . . accurately align two plates, prevent shear stress in fastening screw. Two pins are necessary because screw can not act as aligning-pin.
2 Retained slugs . . . act as pins, perform same function as dowels; are cheaper but not as accurate.
3 A l i g n i n g tube . . . fits into counterbored hole through both parts. Screw clearance must be provided in tube. Milled channel.
Abutment
4 Abutment . . . provides positive, cheap alignment of rectangular part.
Formed
5 Matching channel . . . milled in one part gives more efficient alignment than abutment in preceding method.
Stampings
•Bent flange
A s s e m b l e d
with
Flat
Parts
Slot
Keyhole and lug'
B
6 Bent flange . . . performs similar function as abutment, but may be more suitable where machining or casting of abutment in large part is not desirable or practical.
7 N a r r o w slot . . . receives flange or leg on sheet metal part, allows it to be mounted remote from edge of other part.
Copyright © 2005 by The McGraw-Hill Companies
Bent lug
A
8 Bent lug . . . (A) fits into hole, aligns parts simply and cheaply; or (B) lug formed by slitting clearance hole in sheet metal keys parts together at keyhole.
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Co py rig hte dM ate ria l
Lanced, legs
Stamped
9 Two legs . . . formed by lancing, align parts in manner similar to retained slugs in method 2, but formed legs are only an alternative for sheet too thin to partially extrude slug.
Flat
Bars
B
A
Washer
B
11 Knurled end . . . of round bar (A) has taper which digs into edge of hole when screw is tightened; this gives accurate angular location of bar or sheet. (B) Radial knurling on shoulder is even more positive. Square rod-end
Parts and
Knurled face
Knurled taper
A
10 Aligning projection . . . formed by slitting and embossing is good locating method, but allows a relatively large amount of play in the assembly.
12 Noncircular end . . . on bar may be square (A) or D-shaped (B) and introduced into a similarly-shaped hole. Screw and washer hold parts together as before.
•Pin
13 Transverse pin . . . in rod endfitsinto slot, lets rod end be round but nonrotatable.
Dowel
15 Dowel . . . is simple, efficient method of preventing rotation if rod dta is big enough.
A 14 Washer over square rod end . . . has leg bent to fit in small hole. Washer hole is square, preventing angular movement when all three parts are assembled and fastened with screw and washer.
Copyright © 2005 by The McGraw-Hill Companies
C B 16 Double sheet thickness . * . allows square or hexagonal locating-hole for shaft end to be provided in thin sheet. Extra thickness can be (A) welded (B) folded or (C) embossed.
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V a r i o u s
M e t h o d s
o f
L o c k i n g
T h r e a d e d
M e m b e r s
Co py rig hte dM ate ria l
Locking devices can generally be classified as either form or jam locking. Form locking units utilize mechanical interference of parts whereas the jam type depends on friction developed between the threaded elements. Thus their performance is a function of the torque required to tighten them. Both types are illustrated below.
Unlocked Locked Disk Type Spring
Double Formed Elements
Sheet Metaf Nut
Rcrtchef Type Nu+
Spring Clip
Formed Elemen+s
Ways +0 Use Sefscrews Copyright © 2005 by The McGraw-Hill Companies
BenfTabs Retrieved from: www.knovel.com
Co py rig hte dM ate ria l
Cotters and Safety Wire
Wedge AcKon
Cemerrf- or So Icier
Spring Lock Washers
SpH* Nuts
Jam Nuts
Fiber Inserts
Nut
Bofr
Dondelef (Unlocked) Off-Ana* Thread
7T*t*»tk>nafSer**r&r#$.Co. LocK-Thred Tapered Washer
Self-Locking Thnead©
Copyright © 2005 by The McGraw-Hill Companies
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H
o
w
i n
t o
P r o v i d e
T h r e a d e d
f o r
B a c k l a s h
P a r t s
These illustrations are based on two general methods of providing for lost motion or backlash. One allows for relative movement of the nut and screw in the plane parallel to the thread axis; the other method involves a radial adjustment to compensate for clearance between sloping faces of the threads on each element. Split
Co py rig hte dM ate ria l
Clifford T. Bower
Main nut Locking screw
Screw
'Screw
(A)
(B)
THREE METHODS of using slotted nuts. In (A), nut sections are brought closer together to force left-hand nut flanks to
Index spring
Lead screw
Main nut
Nu1
Adjusting nut
Screw,
•Main nut
MAIN NUT is integral with base attached to part moved by screw. Auxiliary nut is positioned one or two pitches from main nut. The two are brought closer together by bolts which pass freely through the auxiliary nut.
Adjustable section of nut
Screw
Guide s/ot
SELF-COMPENSATING MEANS of removing backlash. Slot is milled in nut for an adjustable section which is locked by a screw. Spring presses the tapered spacer block upwards, forcing the nut elements apart, thereby taking up backlash.
Working nut
Adjusting nut
Bolts
(C)
bear on right-hand flanks of screw thread and vice versa. In (B), and (C) nut sections are forced apart for same purpose.
Spacer block
AROUND THE PERIPHERY of the backlash-adjusting nut are "v" notches of small pitch which engage the index spring. To eliminate play in the lead screw, adjusting nut is turned clockwise. Spring and adjusting nut can be calibrated for precise use.
Auxiliary nut
MQin nut
^-notches
Rubber ring
Adjusting screw
L o cknut
Screw
Locknut
Setscrew
ANOTHER WAY to use an auxiliary or adjusting nut for axial adjustment of backlash. Relative movement between the working and adjusting nuts is obtained manually by the set screw which can be locked in place as shown.
Copyright © 2005 by The McGraw-Hill Companies
Slots Nut bose<
Auxiliary nut
Spring
Setscrews
Screw.
Woinnut
COMPRESSION SPRING placed between main and auxiliary nuts exerts force tending to separate them and thus take up slack. Set screws engage nut base and prevent rotation of auxiliary nut after adjustment is made.
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Co py rig hte dM ate ria l A
C
-S/ots
B>
NUT A IS SCREWED along the tapered round nut, B, to eliminate backlash or wear between B and C, the main screw, by means of the four slots shown.
Spring
Spring
Nut
ANOTHER METHOD of clamping a nut around a screw to reduce radial clearance.
Screw
Split nut
Adjusting nut
AUTOMATIC ADJUSTMENT for backlash. Nut isflangedon each end, has a square outer section between flanges and slots cut in the tapered sections. Spring forces have components which push slotted sections radially inward*
Clamp nut
SPLIT NUT is tapered and has a rounded bottom to maintain as near as possible a fixed distance between its seat and the center line of the screw. When the adjusting nut is tightened, the split nut springs inward slightly.
Screw
Adjustable half Spring
Sere tv
Nut sections
Screw
Screw K
8usht'ng
CLAMP NUT holds adjusting bushing rigidly. Bushing must have different pitch on outside thread than on inside thread. If outer thread is the coarser one, a relatively small amount of rotation will take up backlash.
Adjustable section Dowejs
Adjusting screw
TYPICAL CONSTRUCTIONS based on the half nut principle. In each case, the nut bearing width is equal to the width of the adjustable or inserted slide piece. In the sketch at the extreme left, the cap screw with the spherical seat provides for adjustments. In the center sketch, the adjusting screw bears on the movable nut section. Two dowels insure proper alignment. The third illustration is similar to the first except that two adjusting screws are used instead of only one.
Copyright © 2005 by The McGraw-Hill Companies
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7
S p e c i a l
S
c
r
e
w
A
r
r
a
n
g
e
m
e
n
t
s
How differential, duplex, and other types of screws can provide slow and fast feeds, minute adjustments, and strong clamping action.
Co py rig hte dM ate ria l
Louis Dodge
HtyhiClQSS
/Fvc&/ii/f\
••?7fe£tfs\
Wt^Wts^m
TufntW tufattk
SftiVSiC-
U?d$=XQ
•№№fr
fmmf
n
(no bockia$h)\ j
R$m6yoble\$tdp$
EXTREMELY SM ALL MOVEMENTS. Microscopic ineasiirements, for cxaiii|>le^ are characteristic of this arrange-
S/№,
fcremA\
turns df sjcreiw C»
Screw B
RAPID AND SLOW FEED. With Mu and righthand threads, slide motion with nut locked equals L 4 plus L^ per turn; with nut floating, slide motion ..peir..tUni: equals IIB. • Giet extrenjiel^ fihe.j^^,...^itji. rapid return motion; when threads {are differential.
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l Taperid d/earance Twd-pki support
DIFFERENTIAL CLAMP. 1 his method of using a differential spreyv jto WgWei cjamp jaws combines rugged threads with high clamping power. Clamping pressure, P* "=; Tie/ [H "(jhinf^"HF'jtan" a],'''iviiiere T"4= torqjue Jat Jianaie, R 4'meaft radius of iscrew threads, cj> ^ angle
$Cfkw\A
m
4$ok^0ttdM
BEARING ADJUSTMENT. This screw arrangement is a ^ i i ^ n d ^ ^ a y f o f t p r ^ ^ ing for bearing adjustment and overload protectioiu ,.. '• "...; .L ." ....; .. ..
№
L6pff$pr/n$
'SSW%
H)GH REDUCTION of rotary motion to line linear motion is possible here. Arrangement is for'low forces. Screws are left and right hand. JjA == "L3 phis or minus a small increment. W h m £ £ = •%/10 aftd h-A\ = \ 1/1<M)$ the linear motion of screw A will be 0.05 in. pier turn. When screws are the same hand, linear motion equals LA -h ]L#* \ ' \
Copyright © 2005 by The McGraw-Hill Companies
BACKLASH ELlMINATIONlhelarge screwisloekedand all backlash Is eliminated when the knurled screw is tightened — finger torque is sufficient j
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W o r l d
o f
S e l f - L o c k i n g
S c r e w s
Screws and bolts with self-locking ability are making the scene on more products because of today's emphasis on safety and reliability. Frank Yeaple
will be retained even when the original nut is lost. This roundup of self-locking screws and bolts includes many novel thread forms that are competing for the job of maintaining a tight joint under adverse conditions. Also included are special shank and head designs and the use of plastic inserts and anaerobics to improve self locking characteristics. Variable pitch threads. A screw thread with an oscillating pitch distance can increase and decrease between maximum and minimum values to provide a high resistance to self loosening from shock and vibration. The Leed-Lok
prevailing-torque screw (Fig 1), available from National Lock Fasteners Division of Keystone Consolidated Industries (Rockford, 111.), uses the varying pitch to induce interference on the flanks of the threads. The locking threads need not be produced along the entire length of the screw, but only at desired points. For example, the pitch for a '/2-20 thread may vary as follows: 0.047, 0.050, 0.047. This significantly increases turning friction but does not deform the mating threads beyond their elastic limit. Tilted threads. Another way to induce interference is by deflecting and slightly deforming the threads during the thread
Co py rig hte dM ate ria l
Self-locking ability in fasteners is definitely in. The fear of costly lawsuits stemming from a fastener's loss of clamp load is making manufacturers of products spend a little more time and money to assure joint reliability. Hence design engineers have a freer hand in selecting locknuts and lockscrews. Last month's issue contained a roundup of proprietary types of locknuts. Locknuts are generally cheaper than lockscrews, and fewer special parts (the locknuts) need to be stocked to handle original and replacement parts. But because lockscrews mate with a standard nut, they can provide a better guarantee that the locking system
2. E-Lok threads
1. Leed-lok threads
Conventional thread
Varying pitch
E-Lok thread
Thread configuration for a %-20 thread
4. Tru-Flex threads
3. Vibresist threads
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5. OrIo threads
6. Spiralock threads Wedge ramp
Resilient rib
Co py rig hte dM ate ria l
Nut
Bolt
rolling process when the screws are made. Employed by the Everlock Division (Troy, Mich) of Microdot on its E-Lok screws (Fig 2), the process deflects the 60-deg thread form a certain amount (about 10 deg) from the normal to the screw axis. In general, every two tilted threads are followed by two straight (normal) threads over the chosen length of screw. Partially offset threads. In this method, portion of each thread is deformed parallel to the thread helix axis (Fig 3). As an example, Vibresist screws produced by Russell, Burdsall, & Ward (Mentor, Ohio) provide a consistent prevailing torque, slight or substantial as required. The mating internal threads wedge between the offset screw threads. Spring action is reinforced, and because locking, here as with the other altered-thread types, depends on the elasticity of metal, the screw does not lose its grip at elevated temperatures. The locking threads can be specified adjacent to the head for locking in tapped holes, along the middle of the thread length for locking in tapped holes and near the screw end for locking with standard nuts. Screws with somewhat similarly de7. Lok-Thred threads
Root diameter
Locking root
Nut crest reformed
Tension load on bolt
Bolt root
formed threads are offered by Cleveland Cap Screw (division of SPS Technologies, Cleveland, Ohio) on its Tru-Flex screws (Fig 4). In the process, threads near the end of the screw are specially deformed for a circumference of less than 180 deg of arc. When meshed with conventional female threads, the locking threads are repositioned from root to crest to induce a resisting torque. It was found that reshaping several threads within a 180-deg arc of the fastener circumference would provide ample prevailing torque with only minute changes in pitch diameter. Resilient rib thread. The OrIo thread (Fig 5) has a cold-formed resilient rib on the non-pressureflankof the thread, either part way or continuously around. When a screw with OrIo threads is assembled into a threaded part, the ribs are compressed like springs to force the screw's pressure flanks against the mating threads, and this will increase resistance to rotational forces from vibration or shock. The spring-like action of the rib threads permits the screw to be reused effectively. OrIo threads are available on screws by Holo-Krome Co (West Hartford, Conn)., and Pioneer Starting root
Screw & Nut (Elk Grove Village, 111). Wedge-ramp roots. This internal thread form, called Spiralock (Fig 6), is applied to locknuts and tapped holes to provide locking characteristics to standard bolts. The key innovation is the addition of a 30-deg ramp to the roots of conventional 60-deg threads. When the bolt is seated, the crest of the bolt thread is pulled up tight against the ramp and is wedged firmly with positive metal-to-metal contact that runs the entire length of the nut or tapped hole. The special thread form, in fact, allows wide latitude in bolt tolerances. Spiralock™ locknuts are available from the Greer and the Kaynar divisions of Microdot (Greenwich, Conn.); taps for producing the thread may be obtained from Detroit Tap and Tool Co. (Warren, Mich.) Threads with special wedge-ramp roots also have been applied to screws. In the Lok-thred form (Fig 7), available from Lock Thread Corporation and National Lock Fasteners (Rockford, IU.), the thread of the screw itself performs the locking action. This male thread is shallow, with ample radii and a wide root pitched at a
8. Lamcolok threads
Nut crest
Displaced nut material
Copyright © 2005 by The McGraw-Hill Companies
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10. Chexoff threads
9. Powerlok threads
Meta! compressed by screw
Major diameter
Internal thread
30° locking angle
External thread
Tapped thread major diameter Before 60 a Powerlok thread
Max pitch dia (class 2B)
Co py rig hte dM ate ria l
65% thread minor diameter
After reformation of lobe
60° standard tapped thread
Screw, after tightening
locking angle. These locking roots converge toward the head, A Lok-Thred bolt enters an ordinary tapped hole freely for a few turns, then meets resistance when the bolt root contacts and, by swaging, reforms the nut threads to a perfect fit about the wedge-like locking roots of the bolt. In service, much of the clamp load is carried on the tapered roots, which wedge against the nut crest to lock securely as the work load increases. Bolts which have this type of wedge root thread have a larger root diameter than ordinary threads, which gives strength in tension, torsion and shear, as well as increased endurance limits. Locking roots. A self-locking thread based on flank interference with standard internal thread flanks (Fig 8) provides a clamping force and holding torque that remains constant. Developed by Lamson & Sessions (Cleveland, Ohio), the Lamcolock thread design can be rolled on almost any bolt or screw. It employs a recessed full-radius root and a decreased major diameter giving the thread a wide, squat look. The decreased major diameter provides room for material to flow into
the root recesses, thus averting possible galling. Locking crests. The locking ability of Powerlok screws (Fig 9) is enhanced through the combination of a novel 60 deg - 30 deg thread form and a tri-lobular thread body section. Locking action is developed at the outermost radius of the torque arm of the screw body, whereas most locking screws develop their resistance at lesser radius points. The deeper thread form of the Powerlok geometry, along with a slight increase in the major diameter of the thread as compared to equivalent size conventional screws, also adds to the locking ability. Basically, the nut-thread metal is elastically deformed in the compressed areas created by the 30deg portion of the thread. Powerlok screws are available from several fastener manufacturers, including Continental Screw Co (New Bedford, Mass.), Midland Screw Co. (Chicago, 111.), Central Screw Division of Microdot, and Elco Industries (Rockford, 111.). Resilient bulges. By deforming several threads on one side of the Chexoff screw to form lobes (Fig 10), controlled thread
11. Resilient-bulge threads
interference is induced when the screw is threaded. Available from Central Screw Co, (Des Plaines, 111.), the special screws with lobes create a wedge-like effect by exerting pressures on the opposite side of the mating threads. The lobes may all be located on the same line or else staggered in order to provide considerable periphery pressures. In another design, Deutsch Fasteners Corp. induces a resilient bulge on one side of the bolt (Fig 11) that increases in a similar manner the frictional contact between mating threads on the opposite side of the* bolt. The bulge is formed by the interference action of a precision ball, pressed into a hole drilled close to the minor diameter of the threads during manufacture. Sine-wave threads. In another approach to improving the locking characteristics of bolts, Valley-Todeco, Inc. (SyImar, Calif), has developed its Sine-Lok interference-type thread (Fig 12) for use on the upper regions of a bolt, normally consisting merely of a straight shank. The lower portion of the bolt has conventional threads. During assembly, the bolt shank,
12. Sine-Lok bolt shank
Displaced material
Sine threads Original clearance-hole wall
Copyright © 2005 by The McGraw-Hill Companies
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13. Taper-Lok shank
14. Uniflex head
Co py rig hte dM ate ria l
P = Pressure points
Typical installation
which has a series of modified sine waves, is threaded through the clearance holes of the two parts being assembled, instead of simply being pushed through. The sine wave threads displace the material of the clearance-hole wall into their roots. The protruding, threaded end of the bolt is then tightened by a standard nut. The bolt thus gets a double threading action that helps prevent loosening. Tapered shank. Another way to increase the shank's grip of the parts being assembled together is to provide a slight taper to the shank, as shown in the TaperLok screw by Voi-Shan Division of VSI Corp. (Pasadena, Calif.). (Fig 13). Although only 0.25 in. per linear foot, the taper provides a controlled interference fit that compresses the material of the joint elastically around the hole to induce an excellent preload condition. Head-grip screws. Many new head shapes for screws are designed to increase resistance to vibrational loosening in joints. The Uniflex head (Fig 14), developed by Continental Screw Co. (New 15. Tensiiock head
Bedford, Mass) to complement the company's line of trilobular thread-rolling screws, has a washer-like, undulating head-bearing surface. When the surface, which has three alternate high-and-low areas, is tightened against the joint being assembled, the relieved areas are aligned with potential stress points at the lobes of the trilobular screw thread. As a result of this bearing-area relief, thread engagement is increased and bolt loosening noticeably resisted. High locking power and clamping force are provided with Tensiiock screws available from Eaton Corporation (Massilon, Ohio) (Fig 15). The screw head has a concentric circle of 24 embedded, carburized teeth, with an outer concentric groove that permits flexing of the head to occur. The Durlok fastener available from SPS Technology's Cleveland Cap Screw (Cleveland, Ohio) also has ratchet-like teeth around the periphery of the bearing surface (Fig 16). To limit depth of penetration and marring of the mating surface, the serrations are encircled by a smooth
outer bearing area. Lockscrews with the toothed portion of the head furnished in the form of a preassembled washer include the Melgrip screw by Elco Industries (Rockford, 111) (Fig 17), and Sems screws available from a number of manufacturers, including Shakeproof Division of Illinois Tool (Elgin, 111), National Lock Fasteners (Rockford, 111.), and Central Screw (Fig 18). Melgrip's locking effectiveness results from the mating serrations on the underside of the bolt head and top of the washer surface, coupled by the bidirectional gripping teeth on the periphery of the washer which embed into the joint material. Thus, the washer cannot skid or score. Sems screws are available in a vast variety of washer types to provide spring tensioning for improved loosening resistance, as well as to bridge oversized holes or insulate and protect material surfaces. Nylon-pellet insert. Self-locking screws that use a resilient nylon insert in the threaded section to develop a
16. Durlok head
Carburized teeth
Concentric groove
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17. Melgrip washer-head
18. Sems washer types
Bi-directional gripping teeth
Co py rig hte dM ate ria l
Mating serrations
prevailing-torque locking action (Fig 19) have been a familiar product for a number of years. The nylon pellet, press-fitted into the screw, projects slightly beyond the crest of the thread. Once the threads are engaged, the screw is held in position by lateral pressure. The pellet technique can be applied also to nuts and studs. Screws with nylon-pellet inserts are available from Nylok Fastener Division of USM Corp. (Paramus, NJ.) and ND Industries, Inc. (Troy, Mich.). Nylon fused patch. Another effective and well-established way to help a screw resist loosening is by use of a plastic locking patch that is fused on a dimensionally controlled area of the screw threads, shown in Fig 20. This nylon patch is thickest in the center and feathers-out along the edge to provide a gradual engagement of the locking patch as it encounters mating threads. As the mating threads fully engage the patch, the nylon is compressed to build up a resistance to turning at the right in the figure, and a strong metal-to-metal contact between threads at the
left. This type of screw is available from the Esna Division of Amerace Corp. (Union, N.J.), Long-Lok Fasteners Corp. (Cincinnati, Ohio), Holo-Krome Co., (West Hartford, Conn.), and the Unbrako Division of SPS Industries (Jenkintown, Pa.) Adhesive thread locking. Epoxy and anaerobic adhesives and stiffly viscous fluids have become popular for turning low-cost plain bolts and nuts into lock fasteners. Epoxy, which is a two-part adhesive, is applied in the form of alternating strips or microcapsules to the threaded fastener. Once applied, the epoxy (or one of the anaerobics) remains dormant on the fastener (Fig 21) until a cure is activated by engagement with a mating thread. The curing process for most of the chemical adhesives may continue for days, although by the twelfth hour a good bond has generally been achieved. The adhesive technique, however, does not offer reusability capabilities. Screws with preapplied adhesives are available from ND Industries, (Troy, Mich.), Cleveland Cap
Screw (Cleveland, Ohio) and Camcar Division of Textron (Rockford, 111). Or you can buy your own. Highly viscous fluid coatings, such as Vibra-Tite available from ND Industries (Troy, Mich.) and Oakland Corp., offer a compromise by making the parts adjustable as well as improving self-locking. The user can apply it from a bottle with a brush applicator, like glue. Vibra-Tite, however, is not an adhesive, so its primary usage is not to provide a heavy-duty locking capability; but it does permit the fastener to be assembled, disassembled or adjusted. Prevailing torque. Remember that most self-locking screws rely on friction in one form or another to hold fast against axial or transverse vibration. Transverse vibration is most difficult to protect against because accelerating forces can cause momentary slip at a microscopic level, eventually loosening the thread. Lab and field tests are recommended.
20. Nylon locking-patch screw
21. Adhesive-lock screw
19. Nylon-pellet screw
Strong metal-to-metal contact
Copyright © 2005 by The McGraw-Hill Companies
Compressed nylon
Retrieved from: www.knovel.com
MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION 12
Co py rig hte dM ate ria l
PINS So l ted Sprn ig Pn is Fn id Many Jobs 8 Unusual Jobs for Sprn ig Pn is 8 Electrical Jobs for Sprn ig Pn is 8 More Sprn ig Pn i Appc ilato ins Uses of Split Pn is Desg in Around Spiral Wrapped Pn is A PennyW - sie Connector: The Coter Pn i Standards of So lted-Type Sprn ig Pn is Standards of Coe lid-Type Sprn ig Pn is Standards of Grooved Pn is Standards of RoundH -ead Grooved Drv ie Su tds Standards of Grooved TH -ead Coter Pn is Standards of Coter Pn is Pn i and Shaft of Equal Strength
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
12-2 12-4 12-6 12-8 12-10 12-12 12-14 12-16 12-17 12-18 12-19 12-20 12-21 12-22
S l o t t e d
S p r i n g
P i n s
F i n d
M a n y
J o b s
Assembled under pressure, these fasteners provide powerful gripping action to locate and hold parts together. Robert O. Parmley
Co py rig hte dM ate ria l
Slot should not close
!
!i$in. to 1Z2In. nominal dia
Free
Rods
!
/8 to 51Z2In:
Before insertion
After insertion
Compressed when assembled standard drillsize holes
Tension pin
PiNNINGPARTS
GRIP-SLEEVE
is basic function
action provides external splice
Thin woiI tubing
•Tension pin
Spot weld (optional)
Tension pin
B
Alternate support
Clearance between key and shaft
Tension pin-
Force
B
Tube
A
Pull ring
Force
To weld
Key stock
A
Shaft
Base
Tension pin
LOWCOSTSHAFTSUPPORT
THINWALL TUBING IS STRENGTHENED
is keyed (A), or spot welded (B)
by tension pin at high stress position
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
-Pin sfof -Handle or knob Tension pin
Co py rig hte dM ate ria l
To remove Cose or bos$
•Shaft or turn rod
•Wiring or divider pane!
Tension pin
THINPANELS
•Tension pin
LOWTORQUESHAFT connection, or knob assembly
are inexpensively supported
Crimped sheet metal
Work plate
Tension pin
Plate
Metal or wood
A
Base*
Slide to install
Extend to here without groove
Tension pin
Work plate
Groove optional
Adjustable
Molded plastic
B-
SUPPORTPOSTS PROTECTPROiECTlNGUPS
Copyright © 2005 by The McGraw-Hill Companies
locate (A), provide adjustment (B)
Retrieved from: www.knovel.com
Base Tension pin
8
U n u s u a l
J o b s
f o r
S p r i n g
P i n s
Be sure you get top value from these versatile assembly devices. These examples show how.
Co py rig hte dM ate ria l
Andrew J. Turner
11Ze-in. ~square opening in sheet mefa!
Spring pin
Spring pin'.
Rubber hose, fin O.D.
4- 3/i$ -in. dia. x Un rofipins
A
A
Section 1Ia-A1'
SLOT IN PIN does duty as anchoring device, holding two pieces together. Fastening can be either permanent or temporary. Parts can be metal or non-metal.
Driving gear
Serrated plug Slinger cop Spring pin
PROTECT HYDRAULIC tubing or electrical wires touching sharp edges of casings by clipping pins over the edges of the hole. Its size is only slightly reduced.
Wheel
Frame
Axie
Spring pin
LUBRICANT PASSAGE is combined with retaining pin for gear. Also, stinger ring not only performs functionally but improves appearance too.
Copyright © 2005 by The McGraw-Hill Companies
STIFFEN LIGHT-DUTY structures such as tubular axles with spring pins; they are simple to install and add considerable strength to the assembly.
Retrieved from: www.knovel.com
Co py rig hte dM ate ria l Door
Spring pin
Spring pins
Stationary part in machine.
Wosher
Spring pin
End support or side sheet
TWO PINS SERVE AS HANDLE and
latch. This low-cost assembly replaces an expensive forged handle and a fabricatedmetal latch -piece.
AS BELT GUIDES, spring pins eliminate molded spacers, or costly machined grooves for spacer rings which would otherwise be needed.
Lift screw
Plastic spacer
Bracket ^
Sieeve bearing
5
Zje -in, -dio. spring pin
Spring pins
Li ft-nut
HARDENED STEEL SLEEVE for pivot screw gives durability to legs of folding table illustrated here, while keeping costs competitively low.
Copyright © 2005 by The McGraw-Hill Companies
LOW-COST THREAD in lift-nut can be made by fitting spring pins at correct pitch-positions as shown. Rotate the pins to reduce wear.
Retrieved from: www.knovel.com
8
E l e c t r i c a l
J o b s
f o r
S p r i n g
P i n s
Put these handy assembly devices to work as terminals, connectors, actuators, etc. Andrew J. Turner
Solder
Co py rig hte dM ate ria l
Electronic component
Spring pin
Spring pins
Laminated insulator-board
LOW-COST TERMINALS are made by
AS
assembling two 1 / 16-in.~dia tin-dipped Rollpins into phenolic board. The board should be about 3/32 in. thick.
"patchboard" circuits, spring pins have ample conductivity. Select various circuits by removing or inserting pins,
ELECTRICAL
CONNECTORS in
Printed-circuit board Surfaces for mounting electronic compon-
Wire harness
Spring pin
Plastic
FORMING FIXTURE for wire harnesses is quickly adjusted when different harnessshapes are needed. Plastic sheet has pin holes on !4-in. centers.
Copyright © 2005 by The McGraw-Hill Companies
Spring pin
STAND-OFFS lor printed-circuit boards can be spring pins. Select a pin long enough to ensure adequate spacing between the boards.
Retrieved from: www.knovel.com
Limit switch
Co py rig hte dM ate ria l
Rotating disk
Spring pins
Note with spring pin
Empty hofe
SWITCH ACTUATORS can be quickly relocated in rotating disk if spring pins are employed. Hard steel of pin gives excellent wear resistance,
DRUM-MOUNTED ACTUATORS tune tion in similar way to spring-pin actuators in Fig. 3. Protruding length of pins may he critical, but is easily adjusted.
Extruded aluminum side rails
Spring pin
Support bar
Etched circuit hoard
Bockshelt-
Spring pins
SUPPORT BARS in electronic units can be easily and quickly installed into the sliding chassis with spring pins, Close tolerances are not needed.
Copyright © 2005 by The McGraw-Hill Companies
STRAIN RELIEF t'ov wire in electrical connectors will not slip during assembly. Loop wire then fill shell with potting compound to seal wire in place,
Retrieved from: www.knovel.com
8
M o r e
S p r i n g
P i n
A p p l i c a t i o n s
Some additional ways that these fasteners, assembled under pressure, can grip and locate parts. They can even valve fluids.
Co py rig hte dM ate ria l
Robert O. Parmley
Rubber' or plastic breather tube* \
Slide into place
Drill hole
Tension pin
WorkpiecB
Jig base
Tension pins (guides)
AIr may flow through pin slot
FLEXIBLE BREATHER TUBE is enclosed to pre- j vent swinging and to keep it away from moving machine parts
LOCATE WORRPIECES with this inexpensive jig
•Tension pin
To insert'
Tension pin
Spring \ tension
Coil spring
Check baii
: CHECK-VALVE spring retainer allows maximum flow, is easily adjustable
Copyright © 2005 by The McGraw-Hill Companies
;
'Alternative arrangements ;
HOLD FLATS together for gluing
Retrieved from: www.knovel.com
Base Air flow-slot
Co py rig hte dM ate ria l
To dose off air flow
Plunger , , (ihis can b&housed and spring loaded)
Tension pin
Plastic or \ rubber tube
Metal ftibing
Weld
AIR VALVE is simple yet effective
A-.
Rubber-or* p/osflc fuMng
Tension pHis
B
Adtiesive boiid
ALIGN TUBING for bonding o H j reinforce for strength with internal pin
yfensiw pin
Adjust pins
Tension \pin
Split tubing
Worhpiece
Housing
SPl[IT TUBING IS HELD with tension pin sleeve
Copyright © 2005 by The McGraw-Hill Companies
CONCENTRIC OR ECCENTRIClPOSlIIONING !is quickly adjustable ; J ; ;
Retrieved from: www.knovel.com
U s e s
o f
S p l i t
P i n s
Ten examples show how these pins simplify assembly of jigs and fixtures. The pins are easily removed.
Co py rig hte dM ate ria l
Robert O. Parmley
Jig frame
Split pins
Adjustment bolt
Cam clamp jig
Split pin
Work piece
Work piece
1.
Flat spring
Prevention of spring slippage
Lock blade
2.
Loose fit
Cam pivot and handle
Split pin
Split pin
Frame
Frame (drive fit)
3. Clamp pivot
4.
Support post
Work piece
Split pins
Frame
Stop jaw
5. Anchor for stop jaw
Source: American Machinist, Published by Penton Media, Inc. Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Work piece
Co py rig hte dM ate ria l
Work piece
Split pin (adjustable ht.)
Work piece
Base
Loose fit on arm
Split pins
6. Locator or stop pin
Work piece
Base (pins are drive fit m base)
7. Spring anchor and arm pivot
Locking plote
Split pin
• Fixture base
Drive fit in frame
Frame
Bench
8. Stabilizer for locking plate
'Base halves
Split pin
10. Dowels for fixture base
Split pin
9. Support for post leg
Slotted tubular pins are intended to be forced into their locations; free diameter should be larger than hole diameter so the pin exerts radial force all along its mounting hole to resist axial motion when properly mounted. Maximum compression is controlled by the amount of gap when the pin is free. When it acts as a pivot, the hole through the pivoting member should be a free fit (see figures 7 and 8) so the pin will not be worked loose from its anchor hole. These pins may be made of heat-treated carbon steel, corrosion-resistant steel, or beryllium-copper.
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
D e s i g n
A r o u n d
S p i r a l
W r a p p e d
P i n s
Coil, rolled, or spiral wrapped pins come in a wide range of lengths and diameters. Their applications are limitless; here are eight.
Co py rig hte dM ate ria l
Robert O. Parmley
Fitter tube
Cauiking gun
Spiroi trapped pin
Spirai wrapped pin
Work pressure
Removable jaw
Afount
Pivot. Pm Is a drive fit in the handle housing, and acts as a pivot for trigger
Wood mounting
Hinge pins. is different if the hofe members a
Spiral wrapped pin
Hinge
Screw
If hofe size in both member$ hinge will be free moving; size is the same in both friction hinge is the result
Copyright © 2005 by The McGraw-Hill Companies
Dowel, Here, the dowel acts as a locator anchor pin that can be removed and reused
Pin pivot
"Bushing
Locking member.
Link chain
'Center pin •• •
Link chain connection. Pins are used as pivot or locking members. An advantage: Both types are removable and reusable
Retrieved from: www.knovel.com
Clomp,
Spiral wrapped pin,
Etectrlal wire
Base
Co py rig hte dM ate ria l
Wire gripper. As clamp is tightened In place, pin coils, and secures the wire
Crate
Drive fit*
<$pannep wrench
Comma-shaped area Spiral wrapped pin Bracket
Base
Rotter
Spiral wrapped pin
Lubricated shaft for work roller. Commashaped area of the spiral wrapped pin forms an oil reservoir for the roller
Wrench pin. Coil construction permits pin to fit holes with large tolerances
Forked
Undamped cam fever and reverse, pins wili meet and push plate away from work piece
cam Spirai wrappedk pins
Plate
Slide fit
Drive fit
Work piece Position
Eye bolt
Spiral wrapped pin
Spirai wrapped pin
Spiraf wrapped pins
•Bpse?
Pivot, stop, locator, handle, and anchor are typical applications in the design of a damp, The pins are drive or slide fits, and can be removed and reused if the clamp position must be changed
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
A
P e n n y - W i s e
T h e
C o t t e r
C o n n e c t o r :
P i n
They're simple, inexpensive and make excellent electrical connectors. Why not consider cotter pins the next time you need one?
Co py rig hte dM ate ria l
Robert O. Parmley
Insulated* bundle
Panel ground hole
Blade
Panel
Rubber sleeve
Cotter pin
• Electrical tape
Cord
Screw
Cotter pin
Wire connection-
Wire, woven around cotter pin
Knife blade connector
End mounting connection To contact
Wire
Panel
Coffer pin
Rubber" sleeve
Tie post
Metal base
Coffer pin
Ground wire Ground pin
Tie post and ground connections
Copyright © 2005 by The McGraw-Hill Companies
Glow switch
Retrieved from: www.knovel.com
Cotter pin Glass bulb
Solder
Insulator knob
Cotter pin.
Floor
Co py rig hte dM ate ria l
Wire
Cotter pin
Wire
Joist
Knob anchor pin
Cotter pin
Cotter pin
Cylinder
Wire,
Contactor rod,
Timer-
Rotating cylinder
Pans!
Cylinder contactor
Wire eyelet
Electrical pane!
Cotter pin Panel-
Press tit (alternate)
Base
Standard fit
Electrical panel stabilizer
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Cotter pins
o f
S l o t t e d - T y p e
S p r i n g
P i n s
Co py rig hte dM ate ria l
S t a n d a r d s
Chamfer both ends, contour of chamfer optional
Chamfer both ends, contour of chamfer optional
Break edge
Style 2
Style 1
Optional Constructions
D I M E N S I O N S OF SLOTTED-TYPE SPRING PINS
A
Pin Diameter Nominal Size of Basic Pin Diameter Max. Min. [Note (1)] [Note (2)] [Note (3)]
B Chamfer Diameter
C Chamfer Length
Max.
Max. Min.
Basic
Max.
Min.
F Recommended Stock Hole Size Thickness
Double Shear Load, Min., Ib
Material SAE 10701095 and SAE 51420 SAE 30302 Beryllium [Note (4)] and 30304 Copper
V16 0.062 0.069 Z64 0.078 0.086 3 /32 0.094 0.103
0.066 0.083 0.099
0.059 0.075 0.091
0.028 0.007 0.032 0.008 0.038 0.008
0.012 0.018 0.022
0.065 0.081 0.097
0.062 0.078 0.094
430 800 1,150
250 460 670
270 500 710
Vs 0.125 Z64 0.141 V32 0.156 V16 0.188
0.135 0.149 0.167 0.199
0.131 0.145 0.162 0.194
0.122 0.137 0.151 0.182
0.044 0.044 0.048 0.055
0.008 0.008 0.010 0.011
0.028 0.028 0.032 0.040
0.129 0.144 0.160 0.192
0.125 0.140 0.156 0.187
1,875 2,175 2,750 4,150
1,090 1,260 1,600 2,425
1,170 1,350 1,725 2,600
0.232 0.264 0.330 0.395
0.226 0.258 0.321 0.385
0.214 0.245 0.306 0.368
0.065 0.065 0.080 0.095
0.011 0.012 0.014 0.016
0.048 0.048 0.062 0.077
0.224 0.256 0.318 0.382
0.219 0.250 0.312 0.375
5,850 7,050 10,800 16,300
3,400 4,100 6,300 9,500
3,650 4,400 6,750 10,200
0.459 0.524 0.653 0.784
0.448 0.513 0.640 0.769
0.430 0.485 0.608 0.730
0.095 0.110 0.125 0.150
0.017 0.025 0.030 0.030
0.077 0.094 0.125 0.150
0.445 0.510 0.636 0.764
0.437 0.500 0.625 0.750
19,800 27,100 46,000 66,000
11,500 15,800 18,800 23,200
12,300 17,000
5
9
V32 V4 V16 V8
0.219 0.250 0.312 0.375
V16 V2 V8 V4
0.438 0.500 0.625 0.750
GENERAL NOTE: For additional requirements refer to General Data for Spring Pins on pages 27, 29, and 30 from original document. CHARACTERISTICS SYMBOL Straightness Diameter 0 NOTES: (1) Where specifying nominal size in decimals, zeros preceding the decimal shall be omitted. (2) Maximum diameter shall be checked by GO ring gage. (3) Minimum diameter shall be average of three diameters measured at points illustrated A min =
1+
(4) Sizes % in. (0.625) and larger are produced from SAE 6150H allov steel, not SAE 1070-1095. Reprinted from ASME B18.8.2-2000, by permission of The American Society of Mechanical Engineers. All rights reserved. Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
2+
—-.
o f
C o
N e d - T y p e
S p r i n g
P i n s
Co py rig hte dM ate ria l
S t a n d a r d s
Break edge
Swaged chamfer both ends, contour of chamfer optional
DIMENSIONS OF COILED-TYPE SPRING PINS Double Shear Load, Min., Ib A B C Light Duty Heavy Duty Standard Duty Material Pin Diameter Chamfer RecomStandard Heavy Light mended Hole SAE Nominal Duty Duty Duty Dia. Length SAE Size 1070Size or SAE 10701095 and Basic Pin SAE 1070SAE SAE 1095 and SAE Diameter Max. Min. Max. Min. Max. Min. SAE 30302 1095 and 30302 51420 30302 and SAE [Note [Note [Note [Note [Note [Note [Note 51420 and [Notes and 30304 51420 (D] (2)] (3)] (2)] (3)] (2)] (3)] Max. Ref. Max. Min. (4), (5)] 30304 [Note (5)] 30304 V32 0.031 0.035 0.033 0.039 0.044 0.041 Z64 0.047 0.052 0.049
0.029 0.024 0.032 0.031 0.037 0.024 0.040 0.039 0.045 0.024 0.048 0.047
90 135 190
65 100 145
0.052 0.057 0.054 V16 0.0620.072 0.067 0.070 0.066 0.073 0.067 V 0.0780.088 0.083 0.086 0.082 0.089 0.083 3 64 Z32 0.094 0.105 0.099 0.103 0.098 0.106 0.099
0.050 0.059 0.075 0.091
0.024 0.028 0.032 0.038
0.053 0.065 0.081 0.097
0.051 0.061 0.077 0.093
250 330 550 775
190 265 425 600
475 800 1,150
360 575 825
205 325 475
160 250 360
7
0.106 0.121 0.152 0.182
0.038 0.044 0.048 0.055
0.112 0.129 0.160 0.192
0.108 0.124 0.155 0.185
1,050 1,400 2,200 3,150
825 1,100 1,700 2,400
1,500 2,000 3,100 4,500
1,150 1,700 2,400 3,500
650 825 1,300 1,900
500 650 1,000 1,450
V32 0.219 0.238 0.228 0.235 0.226 0.240 0.228 0.214 V4 0.250 0.271 0.260 0.268 0.258 0.273 0.260 0.243 %6 0.3120.337 0.324 0.334 0.322 0.339 0.324 0.304 % 0.375 0.403 0.388 0.400 0.386 0.405 0.388 0.366
0.065 0.065 0.080 0.095
0.224 0.256 0.319 0.383
0.217 0.247 0.308 0.370
4,200 5,500 8,700 12,600
3,300 4,300 6,700 9,600
5,900 7,800 12,000 18,000
4,600 6,200 9,300 14,000
2,600 3,300 5,200
2,000 2,600 4,000
0.466 0.450 0.471 0.452 0.427 0.095 0.446 0.532 0.514 0.537 0.516 0.488 0.110 0.510 0.658 0.640 0.613 0.125 0.635 0.784 0.766 0.738 0.150 0.760
0.431 0.493 0.618 0.743
17,000 22,500 35,000 50,000
13,300 17,500
23,500 32,000 48,000 70,000
18,000 25,000
3
Z64 0.109 0.120 V 0.125 0.138 8 5 Z 0.156 0.171 3 32 /16 0.188 0.205
V16 0.4380.469 V2 0.500 0.535 V 0.625 0.661 38 /4 0.750 0.787
0.114 0.131 0.163 0.196
0.452 0.516 0.642 0.768
0.118 0.136 0.168 0.202
0.113 0.121 0.130 0.139 0.161 0.172 0.194 0.207
0.114 0.131 0.163 0.196
GENERAL NOTES: (a) For additional requirements refer to General Data for Spring Pins on pages 27, 29,3and 30 from original document, (b) Light-duty SAE 1070 and 1075 pins are not produced in diameters smaller than Z32 in. CHARACTERISTICS SYMBOL Straightness Diameter 0 NOTES: (1) Where specifying nominal size in decimals, zeros preceding the decimal shall be omitted. (2) Maximum diameter shall be checked by GO ring gage. (3) Minimum diameter shall be checked by NO GO ring gage. (4) Sizes V32 in. (0.031) through 0.052 in. are not available in SAE 1070-1095 carbon steel. (5) Sizes % in. (0.625) and larger are produced from SAE 6150H alloy steel, not SAE 1070-1095 carbon steel. Reprinted from ASME B18.8.2-2000, by permission of The American Society of Mechanical Engineers. All rights reserved. Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
o f
G r o o v e d
P i n s
Co py rig hte dM ate ria l
S t a n d a r d s
Type G
groove loc. Type F [Note (5)]
Type E
Type A
both ends typ. Type H [Note (4)]
groove loc.
groove loc.
DIMENSIONS OF GROOVED PINS [Note (1)]
Nominal Size or Basic Pin Diameter [Note (2)]
A
J K H G D F E [Note (3)] [Note (3)] [Note (3)] Neck Neck Shoulder Neck Pilot Chamfer Crown Crown Radius Diameter Length Width Length Length Radius Height Ref Min. Norn. Max. Min. Max. Min. Max. Min. Ref Max. Min. C
Pin Diameter Max. Min,
6 V /32 0.0312 0.0312 0.0297 0.015 V 0.0469 0.0469 0.0454 0.031 V16 0.0625 0.0625 0.0610 0.031 0.0781 0.0781 0.0766 0.031 0.0938 0.0938 0.0923 0.031 V 0.1094 0.1094 0.1074 0.031 V8 0.1250 0.1250 0.1230 0.031 V32 0.1563 0.1563 0.1543 0.062 3 /i6 0.1875 0.1875 0.1855 0.062 7 Z32 0.2188 0.2188 0.2168 0.062 V4 0.2500 0.2500 0.2480 0.062 %e 0.3125 0.3125 0.3105 0.094 % 0.3750 0.3750 0.3730 0.094 0.4375 0.4375 0.4355 0.094 V2 0.5000 0.5000 0.4980 0.094
0.005 0.005
0.0065 0.0087
0.088 0.068 0.104 0.084
0.005 0.005 0.005 0.005
0.0091 0.0110 0.0130 0.0170
0.135 0.150 0.166 0.198
0.016 0.016 0.016 0.031
0.0180 0.0220 0.0260 0.0340
0.260 0.291 0.322 0.385
0.031 0.031 0.031
0.0390 0.0470 0.0520
0.067 0.082 0.088 0.109
0.057 0.072 0.078 0.099
0.130 0.151 0.172 0.214 0.135 0.125 0.062 0.255 0.135 0.125 0.094 0.298 0.135 0.125 0.094 0.317
0.120 0.141 0.162 0.204
0.028 0.028 0.059 0.059
0.041 0.041 0.041 0.057
0.059 0.091 0.091 0.122 0.479 0.459 0.132 0.122 0.541 0.521 0.195 0.185 0.635 0.615 0.195 0.185
0.057 0.072 0.072 0.104
0.115 0.130 0.146 0.178
0.240 0.271 0.302 0.365
0.038 0.038 0.069 0.069 0.069 0.101 0.101 0.132
0.031 0.031 0.031 0.047
0.047 0.062 0.062 0.094
0.016 0.016 0.031 0.031 0.031 0.047 0.047 0.062
0.245 0.288 0.307
GENERAL NOTE: For additional requirements and recommended hole sizes see Section 7 from original document. NOTES: (1) For expanded diameters applicable to pins made from corrosion resistant steel or monel, see Table 6B; and for pins made from other materials, see Table 6A. (2) Where specifying3nominal size in decimals, zeros preceding decimal and in the fourth decimal place shall be omitted. (3) Pins in V32 and /64 in. sizes of any length and all sizes V4 in. nominal length, or shorter, are not crowned or chamfered. See para. 7.4 of General Data. Alloy steel pins of all types shall have chamfered ends conforming with Type F pins, included within the pin length. (4) Type H replaces Types B and D as previously used in ANSI B18.8.2-1978 (see Appendix C). (5) Type F replaces Type C as previously used in ANSI B18.8.2-1978 (see Appendix C). (6) Non-stock items — not recommended for new design. Reprinted from ASME B18.8.2-2000, by permission of The American Society of Mechanical Engineers. All rights reserved. Copyright © 2005 by The McGraw-Hill Companies
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S t a n d a r d s
R o u n d - H e a d
G r o o v e d
S t u d s
Co py rig hte dM ate ria l
D r i v e
o f
K x 25° Chamfer
DIMENSIONS OF ROUND-HEAD GROOVED DRIVE STUDS
A Stud Size Number Shank and Basic Diameter Shank Diameter [Note (1)] Max. Min.
C)
P
Head Dianieter
Head Height
Max.
Min.
Max.
Min.
V8
3
/16
B Expanded Diameter ± 0.002 Nominal Stud Length [Note (2)] 5 V2 V4 % % /ie
K Chamfer
%
Min.
0 0.067 0.067 0.065 0.130 0.120 0.050 0.040 0.074 0.074 0.074 2 0.086 0.086 0.084 0.162 0.146 0.070 0.059 0.096 0.096 0.095 4 0.104 0.104 0.102 0.211 0.193 0.086 0.075 0.115 0.113 0.113
0.005 0.005 0.005
6 0.120 0.120 0.118 0.260 0.240 0.103 0.091 7 0.136 0.136 0.134 0.309 0.287 0.119 0.107 8 0.144 0.144 0.142 0.309 0.287 0.119 0.107
0.005 0.005 0.005
10 12 14 16
0.161 0.196 0.221 0.250
0.161 0.196 0.221 0.250
0.159 0.194 0.219 0.248
0.359 0.408 0.457 0.472
0.334 0.382 0.429 0.443
0.136 0.152 0.169 0.174
0.132 0.130 0.130 0.147 0.147 0.144 0.155 0.153 0.153
0.124 0.140 0.156 0.161
0.173 0.171 0.171 0.206 0.204 0.204 0.234 0.232 0.232 0.263
0.016 0.016 0.016 0.016
GENERAL NOTE: For additional requirements and recommended hole sizes refer to General Data for Grooved Pins, also Grooved Drive Studs and Grooved T-Head Cotter Pins on pages 18, 19, 26, and 27 from original document. NOTES: (1) Where specifying stud size in decimals, zeros preceding decimal and in the fourth decimal place shall be omitted. (2) Sizes and length, for which B values are tabulated are normally readily available in carbon steel. For other size-length combinations or materials, manufacturers should be consulted.
PILOT LENGTH DIMENSIONS FOR ROUND-HEAD GROOVED DRIVE STUDS
Nominal Size 0 2 16 4 6 14 7 8 10 12 Nominal M, Pilot Length Length Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. V8 0.051 0.031 0.051 0.031 3 Z16 0.067 0.047 0.067 0.047 0.067 0.047 V4 0.082 0.062 0.082 0.062 0.082 0.062 0.082 0.062 S 0.098 0.078 0.098 0.078 0.098 0.078 /,6 3
Z8 V2 % 3 Z4
0.114 0.094 0.114 0.094 0.114 0.094 0.114 0.094 0.114 0.094 0.14 0.12 0.14 0.12 0.14 0.12 0.14 0.12 0.14 0.12 0.14 0.12 0.18 0.16 0.18 0.16 0.18 0.16 0.18 0.16 0.20 0.18 0.20 0.18
GENERAL NOTE: To find total pilot length of lengths (L) not shown above, use the next shorter length. Reprinted from ASME B18.8.2-2000, by permission of The American Society of Mechanical Engineers. All rights reserved. Copyright © 2005 by The McGraw-Hill Companies
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o f
G r o o v e d
T - H e a d
C o t t e r
Co py rig hte dM ate ria l
S t a n d a r d s
P i n s
DIMENSIONS OF GROOVED T-HEAD COTTER PINS [Note (1)]
Nominal Size or Basic Shank Diameter [Note (2)] 5 Z32 3 Z16 1 Z4
0.156 0.187 0.250
5 Z16 23 Z64 1 Z2
0.312 0.359 0.500
A
N
O
P
Q
Length Max.
Head Diameter Max. Min.
Head Height Max. Min.
Head Width Max. Min.
Shank Diameter Max. Min.
B Expanded Shank Diameter Max. Min.
0.154 0.186 0.248
0.150 0.182 0.244
0.168 0.201 0.265
0.163 0.195 0.258
0.08 0.09 0.12
0.26 0.30 0.40
0.24 0.28 0.38
0.11 0.13 0.17
0.09 0.11 0.15
0.18 0.22 0.28
0.15 0.18 0.24
0.161 0.193 0.257
0.156 0.187 0.250
0.310 0.358 0.498
0.305 0.353 0.493
0.326 0.375 0.520
0.320 0.369 0.514
0.16 0.18 0.25
0.51 0.57 0.79
0.48 0.54 0.76
0.21 0.24 0.32
0.19 0.22 0.30
0.34 0.38 0.54
0.30 0.35 0.49
0.319 0.366 0.508
0.312 0.359 0.500
Recommended Hole Size Min. Max.
GENERAL NOTE: For additional requirements refer to General Data for Grooved Pins, also Grooved Drive Studs and Grooved T-Head Cotter Pins on pages 18, 19, 26, and 27 from original document. NOTES: (1) For groove lengths, M, which vary with pin length, see Table 8A. (2) Where specifying nominal size in decimals, zeros preceding decimal and in the fourth decimal place shall be omitted.
GROOVE LENGTH DIMENSIONS FOR GROOVED T-HEAD COTTER PINS
Max.
Min.
Nominal Size 5/ Z4 Zi6 M, Pilot Length [Note (D] Max. Min. Max. Min.
0.50 0.50 0.62 0.68
0.48 0.48 0.60 0.66
0.62 0.68
0.60 0.66
0.75
0.73
0.75 0.88
0.73 0.86
5/ /32
Nominal Length 3 Z4 7 Z8
11 1Z8 1V4 11Z2 13/4 2 211Z4 23Z2 2 /4 3
Max. 0.50 0.50 0.62 0.68
3/ /16
Min. 0.48 0.48 0.60 0.66
23/ /64
1
0.68
0.66
0.75 0.88 1.00 1.25
0.73 0.86 0.98 1.23
1
Z2
Max.
Min.
Max.
Min.
0.75 0.88 1.00 1.25
0.73 0.86 0.98 1.23
1.25
1.23
1.31 1.50 1.62 1.85
1.29 1.48 1.60 1.83
NOTE: (1) Sizes and lengths for which M values are tabulated are normally readily avilable. For other size-length combinations, manufacturers should be consulted. Reprinted from ASME B18.8.2-2000, by permission of The American Society of Mechanical Engineers. All rights reserved. Copyright © 2005 by The McGraw-Hill Companies
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o f
C o t t e r
P i n s
Co py rig hte dM ate ria l
S t a n d a r d s
Plane of contact with gage
Extended Prong Square Cut Type
Hammer Lock Type
DIMENSIONS OF COTTER PINS
Nominal Size1-2 or Basic Pin Dia. y bz 0.031 %4 0.047 1 A6 0.062 %4 0.078 %2 0.094 0.109 0.125 %4 0.141 %2 0.156 ^16 0.188 0.219 V4 0.250 0.312 % 0.375 A6 0.438 0.500 % 0.625 0.750
7
Total Shank Diameter A3
Extended Prong Length D Min. 0.01 0.02 0.03 0.04 0.04
Gage Hole Diameter ±0.001 0.047 0.062 0.078 0.094 0.109
Max. 0.032 0.048 0.060 0.076 0.090
Min. 0.028 0.044 0.056 0.072 0.086
Max. 0.032 0.048 0.060 0.076 0.090
Min. 0.022 0.035 0.044 0.057 0.069
Head Diameter C Min. 0.06 0.09 0.12 0.16 0.19
0.104 0.120 0.134 0.150
0.100 0.116 0.130 0.146
0.104 0.120 0.134 0.150
0.080 0.093 0.104 0.116
0.22 0.25 0.28 0.31
0.05 0.06 0.06 0.07
0.125 0.141 0.156 0.172
0.176 0.207 0.225 0.280
0.172 0.202 0.220 0.275
0.176 0.207 0.225 0.280
0.137 0.161 0.176 0.220
0.38 0.44 0.50 0.62
0.09 0.10 0.11 0.14
0.203 0.234 0.266 0.312
0.335 0.406 0.473 0.598 0.723
0.329 0.400 0.467 0.590 0.715
0.335 0.406 0.473 0.598 0.723
0.263 0.320 0.373 0.472 0.572
0.75 0.88 1.00 1.25 1.50
0.16 0.20 0.23 0.30 0.36
0.375 0.438 0.500 0.625 0.750
Wire Width B
GENERAL NOTE: For additional requirements, refer to General Data for Cotter Pins in Sections 1 and 3 from original document. NOTES: (1) Where specifying nominal size in decimals, zero preceding decimal shall be omitted. (2) %4, %2,7Ae and % not preferred for new design. (3) Total shank diameter, A dimension, is two times wire thickness. A is measured at end of pin where no gap is permitted.
Reprinted from ASME B18.8.2-2000, by permission of The American Society of Mechanical Engineers. All rights reserved. Copyright © 2005 by The McGraw-Hill Companies
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P i n
a n d
S h a f t
o f
E q u a l
S t r e n g t h
THE
Co py rig hte dM ate ria l
Herman J. Scholtze
ACCOMPANYING
TABLE
gives
the
sizes of round driving pins and round shafts drilled to receive the pin in which both parts are equally strong in shear, for the condition that the shaft and pin are made of the same material. The author has discovered that when the pin diameter equals 40 percent of the shaft diameter, the shearing stress in the pin equals the shearing stress in the shaft, also that the polar moment of inertia of the drilled shaft equals the shaft radius to the fourth power. Values given in the table in columns headed "Torque," and "Load on One End of Pin" have been computed for a shear stress of 12,000 Ib. per sq. in. For other values of shear stress, the load on one end of pin equals the cross-section area of the pin multiplied by the allowable shear stress, and the torque equals the load on the pin multiplied by the shaft diameter. R r S» Sp /
sa radius of shaft, in. — radius of pin, in. = shearing stress in shaft, Ib. per sq. in. = shearing stress in pin, Ib. per sq. in. = polar moment of shaft cross-section through the axis of pin bore Tt — torque on shaft, in. Ib. Tp — torque delivered by pin, in. Ib. 0 =» central angle subtended by one half the chord of circular segment section or drilled shaft, radians
Equal Strength Shafts and Pins of Similar Material
Dia. of Shaft, in. D
1/4 5/16 3/8 7/16 1/2 5/8 3/4
1W 1-1/4 1-1/2 1-3/4 2 2-1/4 2-1/2 2-3/4 3 3-1/2 4 4r-l/2 5-1/2 6 7 8 9 10 11 12
Dia. of Pin, in. d
Polar Moment of Inertia, U
0.000244 0.100 0.000597 0.125 0.001236 0.150 0.002290 0.175 0.003906 0.200 0.009537 0.250 0.01977 0.300 0.03663 0.350 0.06250 0.400 0.1526 0.500 0.3164 0.600 0.5862 0.700 1.0000 0.800 1.6018 0.900 2.4414 1.00 3.5745 1.10 5.0625 1.20 9.3789 1.40 16.000 1.60 25.629 1.80 39.062 2.00 57.191 2.20 91.000 2.40 150.062 2.80 256.000 3.20 410.062 3.60 625.000 4.00 915.062 4.40 4.80 1,296.000
Copyright © 2005 by The McGraw-Hill Companies
Polar Section Modulus, J/R
0.001952 0.003820 0.006579 0.01047 0.01562 0.03051 0.05273 0.08374 0.1250 0.2442 0.4218 0.6700 1.0000 1.4238 1.9531 2.6000 3.3750 5.3593 8.0000 11.390 15.625 20.797 27.000 42.875 64.000 91.125 125.000 166.375 216.000
CrossTorque, Section Load in. Ib. at on One Axea of 12,000 Ib. End of One End per sq. in. of Pin, Shear Stress Pin, Ib. P = T/D sq. in. T 23.5 45.8 79 125 187 366 635 1,010 1,500 2,940 5,100 8,000 12,000 17,000 23,400 31,200 40,500 64,000 96,000 125,000 187,000 240,000 324,000 515,000 770,000 1,090,000 1,500,000 2,000,000 2,600,000
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94 146 210 286 374 590 845 1,160 1,500 2,350 3,400 4,570 6,000 7,550 9,350 11,350 13,500 18,200 24,000 27,700 37,500 43,750 54,000 73,500 96,000 121,000 150,000 182,000 216,000
0.00785 0.01277 0.01767 0.02405 0.03142 0.04909 0.07069 0.09621 0.1257 0.1963 0.2827 0.3848 0.5027 0.6362 0.7854 0.9500 1.131 1.539 2.011 2,545 3.142 3.801 4.524 6.158 8.042 10.18 12.57 15.21 18.10
MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
13
Co py rig hte dM ate ria l
SPRINGS 12 Ways to Put Sprn igs to Work Mutlp ie l Uses of Coli Sprn igs Control Deph t Prm i er Tool Empo lys Coli Sprn igs One Sprn ig Returns the Hand Lever 6 More One Sprn ig Lever Return Desg ins How to Stifen Beo lws wtih Sprn igs Sprn igs: How to Desg in for Vara ibe l Rate Adu jstabe l Extenso in Sprn igs Compresso in Sprn ig Adu jsm t ent Meh tods I Compresso in Sprn ig Adu jsm t ent Meh tods Il Flat Sprn igs in Mechansims Flat Sprn igs Fn id More Work Pneumacit Sprn ig Ren io frcement
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13-2 13-4 13-6 13-8 13-10 13-12 13-14 13-16 13-18 13-20 13-22 13-24 13-26
1 2
W a y s
t o
P u t
S p r i n g s
t o
W o r k
Variable-rate arrangements, roller positioning, space saving, and other ingenious ways to get the most from springs.
Co py rig hte dM ate ria l
L. Kasper
Lighter spring
VARIABLE RATE with sudden change from light load to heavy load is achieved by limiting the low-rate extension with a spring.
Heavier spring-
DIFFERENTIAL-RATE linkage lets actuator stroke be under light tension at start, then gradually heavier tension. Support bracket is attached toa slide, which operates platen
Wheel- center movement
COMPRESSING MECHANISM has dual rate for double-action compacting. In one direction pressure is high, in reverse pressure is low.
Slide Slide movement
Spring movement
SHORT EXTENSION of spring for long movement of slide keeps tension change between maximum and minimum low. Tube reciprocates in operation
Hopper-
Springe gripspin
CLOSE-WOUND SPRING is attached to a hopper and will not buckle when used as a movable feed-duct for nongranular material.
Copyright © 2005 by The McGraw-Hill Companies
Guided wire
PIN GRIP is spring that holds pin by friction against end movement or rotation, but lets pin be repositioned without tools.
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springs
Co py rig hte dM ate ria l
Different-rate
THREE-STEP RATE change at predetermined positions. The lighter springs will always compress first regardless of their position.
Roller
Spring grips shaft
ROLLER POSITIONING by tight-wound spring on shaft obviates necessity for collars. Roller will slide under excess end thrust.
SPRING WHEEL helps distribute deflection over more coils than if spring rested on corner* Less fatigue and longer life result. THting lever
Other end of spring attached to brake lever
INCREASED TENSION for same movement is gained by providing a movable spring mount and gearing it to the other movable lever.
L ever in operating position
Brokeapplying lever
Lever tilts
Fixed plate
Lever in neutral position
Spring pressure holds lever in neutral position
Cam surfaces
Brake-applying shaft
TENSION VARIES at different rate when brake-appl\ing lever reaches the position shown* Rate is reduced when tilting lever tilts.
Copyright © 2005 by The McGraw-Hill Companies
TOGGLE ACTION here is used to make sure the gear-shift lever will not inadvertently be thrown past neutral,
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M u l t i p l e
U s e s
o f
C o i l
S p r i n g s
Co py rig hte dM ate ria l
R. O. Parmley
CUT-A-WAY VE IW
Coil Spring
Float
Coil Spring used to soften impact of float in teat cup washing mechanism
Coil Spring
Coil Spring used as reinforcement of filter sock in milk filter assembly
Source: Bender Machine Works, Inc. Copyright © 2005 by The McGraw-Hill Companies
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B-X CABLE
SOLENOID VALVE
Co py rig hte dM ate ria l
VACUUM
Coil Spring
WALL .
TO TROL-O-MATIC WALL BRACKET
• TWO-WAY VALVE
MOUNTED VIEW
END
Coil Spring used stabilizing component in two-way valve assembly Source: Bender Machine Works, Inc.
Coil Spring
BALL-
Coil Spring serve as controls for bullet valve and ball valve
O-RING
BULLET VALVE
Copyright © 2005 by The McGraw-Hill Companies
Coil Spring
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C o n t r o l
D e p t h
P r i m e r
C o i l
S p r i n g s
E m p l o y s
T o o l
Co py rig hte dM ate ria l
E. E. Lawrence, Inventor R. O. Parmley, Draftsman
Coil Spring
Coil Spring
Coil Spring
/6 (Bullet Casing)
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l
V i e w "A-A"
Coil Spring
"A"
Coil Spring
Coil Spring
"A"
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O
n
e
S
p
r
i
n
g
R
e
t
u
r
n
s
t h e
H
a
n
d
L
e
v
e
r
These seven designs need only a single spring—compression, extension, flat or torsion.
Co py rig hte dM ate ria l
L. Kasper
1
Slide bar
Spring holder
SLIDE BAR attached to lever compresses spring against pressure pins in either direction. Guide pins in spring holder hit end of slot to limit movement.
Pressure pins Guide pins
Spring anchors
Stop
Slotted lug
Flat spring
Stop.
3
2 FLAT SPRING has initial tension which gives positive return for even a small lever-movement.
CLOSE-WOUND HELICAL SPRING gives almost constant return force. Anchor post for spring also acts as limit stop.
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l
Collar
Pressure lever
Free fit
4
Spring anchor
Idle gear
PRESSURE LEVER returns hand lever because it rotates on a different center. Collar sets starting position.
5
GEARS extend spring when lever moves up to 180° in either direction.
Guide pins
Button
Slide bor>
Spring anchor
Stop
Anchor pin
6
SLIDE BAR rides on guide pins as lever pushes it to right. Stretched spring pulls slide bar against lever to return lever to vertical position.
7 OPEN-WOUND HELICAL SPRING extends inside shaft
of handle. Coils must be wound in direction of movement so that spring tightens instead of unwinds as lever turns.
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6
M
o
r
e
O
n
e
S p r i n g
L e v e r
R e t u r n
D e s i g n s
A flat, torsion or helical spring does the job alone.
Co py rig hte dM ate ria l
L. Kasper
Flat spring
Swivel bar
Fixed pin
2
HIGHER SPRING RATE, when the projec-
tion hits the flat spring, warns operator he's approaching end of travel and assures quick disengagement.
1 SWIVEL BAR, which slides on fixed pin, returns hand lever. Slot in swivel bar is limit stop for movement either way.
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l
Pressure lever
Allowance for spring con fraction
4
Fulcrum pins
3
Torsion spring
TORSION SPRING must have coil diameter larger than shaft diameter to allow for spring contraction during windup.
DOUBLE PRESSURE-LEVER returns handle to center from either direction by compressing spring. Lever pivots on one pin and comes to stop against the other pin.
Spring lever'
Anchor post
Stop pin-
Idle gear
Liff pins
Anchor post 6
5
LEVER flops to stop because of spring pull. Stoppins inside springs limit movement.
Copyright © 2005 by The McGraw-Hill Companies
SELF-CENTERING HAND LEVER returns to vertical as soon as it's released. Any movement lifts spring lever and -creates a righting force.
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H o w
t o
S t i f f e n
B e l l o w s
w i t h
S p r i n g s
Rubber bellows are an essential part of many products. Here are eight ways to strengthen, cushion, and stabilize bellows with springs. Robert O. Parmley
Co py rig hte dM ate ria l
Cop,
. Top cap
Rubber bellows
Coil spring
Bellows action
Action
Rubber bellows
Connection tube Housing
C~rod
Toperea coil spring
Flat washer
Adjustment nut Stem Adjustable distance
Cnamber base
INTERNAL COIL SPRING strengthens and adds vertical stability. To install spring, just "corkscrew" it into place. ;. .}
Top-cap
Loop tn rod \
CUSHION BELLOWS SUPPORT-ROD with coil spring. Adjustment is provided and bellows are strengthened by this arrangement*
Adhesive bond (it necessary/
Top cap
Zuboer_ '•bellows
Rubber^ bellows
Adhesive bond ;
Action distance
Aligning -pin
Cott spring
Compression . spring
Breather holes .
AT heIeS COMPRESSION STRENGTH for bellows is best obtained with a coil spring, mounted internally as shown.
Copyright © 2005 by The McGraw-Hill Companies
INTERNAL RIGIDITY of bellows is here provided by a mating rod and sleeve i n which a compression spring is fitted.
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Connection rod
Adjustment nut
Co py rig hte dM ate ria l
Rubber bellows
Compression clearance for bellows
COtJ:
spring
:
Top cap
Coil spring
Top cap-
Cot I spring
Rubber bellows Housing
Rubber bellows
Base
EXTERNAL STABILITY is provided here, with the added advantage of simple assembly that strengthens bellows, too.
ADJUSTMENT WITH TENSION SPRING lets bellows be enclosed in casting while adjustment is provided externally.
Connecting air hose
Air tube
\Rubber • bellows
Rubber bellows
Coil_ spring
Frame
Float plate
Anchor pin
Coil springs
Air hole
Base
BELLOWSSTIFFENERANDSTABILIZER are sometimes combined by means of a platform and four mounting springs.
Copyright © 2005 by The McGraw-Hill Companies
Air hole
HOUSED STIFFENING UNIT gives solid mount for hose connection, together with spring action for bellows.
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S p r i n g s :
H o w
t o
D e s i g n
f o r
V a r i a b l e
R a t e
Eighteen diagrams show how stops, cams, linkages and other arrangements can vary the load/deflection ratio during extension or compression.
Co py rig hte dM ate ria l
James R Machen
1 WITH TAPERED-PITCH SPRINGS
(1), the number of effective coils changes with deflection—the coils "bottom" progressively. Tapered
2
3
O.D. and pitch (2) combine to produce similar effect except spring with tapered O.D. will have shorter solid height.
IN DUAL SPRINGS one spring closes solid before the other.
STOPS (4, 5) can be used with either compression or extension springs.
4
5
Adjustment screws
6
8
7
LEAF SPRINGS (6, 7, 8) can be arranged so that their effective lengths change with deflection.
Copyright © 2005 by The McGraw-Hill Companies
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Constant force 10 TORSION SPRING combined with variable-radius pulley gives constant force.
Moment arm
9
Co py rig hte dM ate ria l
Torsion spring
CAM-AND-SPRING DEVICE causes torque relationship to vary during rotation as moment arm changes.
LINKAGE-TYPE ARRANGEMENTS (11, 12) are often used in instruments where torque control or antivibration suspension is required.
ii
12
14
MOLDED-RUBBER SPRING has deflection characteristics that vary with its shape.
13
15
ARCHED LEAF-SPR1NG gives almost constant force when shaped like the one illustrated.
4-BAR MECHANISM in conjunction with a spring has a great variety of load/deflection characteristics.
16 TAPERED MANDREL AND TORSION SPRING. Effective number of coils decreases with torsional deflection.
Copyright © 2005 by The McGraw-Hill Companies
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A
d
j
u
s
t
a
b
l
e
E
x
t
e
n
s
i
o
n
S
p
r
i
n
g
s
Henry Martin
Design of the end of a tension or extension Ffaf
spring using some form of loop integral with the spring is often unsatisfactory, since many Fl G. 1
spring failures occur somewhere in the loop,
Co py rig hte dM ate ria l
FIG.3
most often at the base of the loop adjacent to the spring body.
Use of the accompanying
tested methods has reduced breakage and there-
fore down-time of machinery, especially where adjustability of tension and length is required
Fl 6.2
FIG. 1—Spring-end is tapered about a loop made of larger diameter and somewhat softer wire than that used for the spring. Upper end of wire is also formed into a loop, larger and left open to engage a rod-end or eye-bolt A.
FIG.4
Fiat
FIG. 2—A loop is formed at the end of a soft steel rod threaded at the opposite end for a hex adjusting nut. Ordinary threaded rod-end may be substituted if desired.
FIG.5
FIG.7
FIG. 3—End of adjusting screw is upset in shape of a conical head to coincide with taper of spring-end. Unless initial tension of spring is sufficiently great a wrench fiat on stem is provided to facilitate adjustment. FIG. 4—The last coil of spring is bent inwardly to form hoop A which engages slot in nut. Although a neat and simple design, all spring tension is exerted on hook at one point, somewhat off-center of spring axis. Not recommended for heavy loads. FIG. 5—An improved method over Fig. 4. The nut is shouldered to accommodate two end coils which are wound smaller than the body of spring. Flats are provided for use of wrench during adjustment.
FIG.6
FIG. 6—When wire size permits, the spring end can be left straight and threaded for adjustment. Because of the small size of nut a washer must also be used as shown. FIG. 7—The shouldered nut is threaded with a coarse V-thread and is screwed into the end of the spring. The point of tangency between the 30-deg. side of thread and wire diameter should be such that the coils cannot pull off. The end of the spring is squared for sufficient friction so that nut need not be held when turning the adjusting screw.
Fl G. 8
FIG. 8—For close-wound extension springs, end of rod may be threaded with a shallow thread the root of which is the same curvature as that of the spring wire. This form of thread cut with the crests left sharp provides greater engagement contact.
FIG.9
FIG. 9—For more severe duty, the thread is cut deeper than that shown in Fig. 8. The whole spring is close-wound, but when screwed on adjusting rod, the-coils are spread, thereby creating greater friction for better holding ability. Spring is screwed against the relieved shoulder of rod.
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FIG. 10—When design requires housed spring, adjusting rod is threaded internally. Here also, the close-wound coils are spread when assembled. Unless housing bore is considerably larger than shouldered diameter of adjusting rod, or sufficient space is available for a covered spring, methods shown in Figs. 8 or 9 will be less expensive.
Co py rig hte dM ate ria l
FIG. 11—A thin piece of cold-drawn steel is drilled to exact pitch of the coils with a series of holes slightly larger than spring wire. Three or four coils are screwed into the piece which has additional holes for further adjustment. It will be seen that all coils so engaged are inactive or dead coils.
FIG.10
FIG. 12—A similar design to that shown in Fig. 11, except that a smaller spring lies inside the larger one. Both springs are wound to the same pitch for ease of adjustment. By staggering the holes as shown, the outer diameter of the inner spring may approach closely that of the inner diameter of the outer spring, thereby leaving sufficient space for a third internal spring if necessary. FIG. 13—When the spring is to be guarded, and to prevent binding of the spring attachment in the housing, the end is cross-shaped as shown in the section. The two extra vanes are welded to the solid vane. The location of the series of holes in each successive vane is such as to advance spring at one quarter the pitch.
FIG.11 X
Fie. 14-This spring end has three vanes and is turned, bored and milled from solid round stock where welding facilities are not convenient. In sufficient quantities, the use of a steel casting precludes machining bar stock. The end with the hole is milled approximately 1 A in. thick for the adjusting member.
X
Y
FIG.I2
Section X-X
FIG. 15—A simple means of adjusting tension and length of spring. The spring anchor slides on a plain round rod and is fastened in any position by a square head setscrew and brass clamping shoe. The eye in the end of the spring engages a hole in the anchor. FIG. 16—A block of cold-drawn steel is slotted to accommodate the eye of the spring by means of a straight pin. The block is drilled slightly larger than the threaded rod and adjustment and positioning is by the two hex nuts. FIG. 17—A similar arrangement to that shown in Fig. 16. The spring finger is notched at the outer end for the spring-eye as illustrated in the sectioned end view. In these last three methods, the adjustable member can be made to accommodate 2 or 3 springs if necessary.
Y
FIG.13
Section Y-Y
X
X
FIG.I4
FIG.16
Section 2-1
FIG. 17
FIG.15
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C o m p r e s s i o n A d j u s t m e n t
S p r i n g
M e t h o d s
I Slotted or socket head locking screw
Co py rig hte dM ate ria l
In many installations where compression springs are used, adjustability of the spring tension is frequently required. The methods shown incorporate various designs of screw and nut adjustment with numerous types of spring-centering means to guard against buckling. Some designs incorporate frictional reducing members to facilitate adjustment especially for springs of large diameter and heavy wire.
Spanner nut, split on opposite side
Henry Martin
FIG.3
Cose
Peened
Spring centering seats For spanner wrench; knurl if for light duty Lock nut
Hotlow-head screw turned down
Spring centering seats
FIG.I
Adjusting nut
FI6.2
Adjustment nut
Spring retaining washer
Movable lever
Conical spring seats
Stationary frame
Spring centering seats
lock nut
Adjusting screw
FIG.5
FIG.4
Stationary bosses,
Pin
Pivot
Adjusting nuf
Adjusting nuts
Centering horn
Flanged spring seat
FlG.6
Movable flange
Ad/us fable spring seat
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FIG.7
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Stationary rod
Guard Adjusting screw Tongen tial pin Clearance Less clearance Recessed spring retainer
Co py rig hte dM ate ria l
Centering arrangement
Adjusting •w screw
Spring seat and centering cup Adjusting nut
Pin
FIG.8
Lock nut
Spring seat
Spring seat
Case
FIG.9
Adjustment for Adjusting other mechanism screw
FIGJO
Stationary rod and flange
Pin
Locking pin
Drilled holes for spring adjustment Stamped spring seat pin FIGJ2
FIGJl
Adjusting screw
Spring centers
FlG.13 Lock nut if required Pounded to equalize spring pressure hardened pivot and conical seat Slide fit
Plates may be counterbored instead of hollow milled to hold springs
Slotted head
Press fit
FIG.14
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FIG.15
Hardened pivot and conical seat
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Adjustment screw
C o m p r e s s i o n A d j u s t m e n t
S p r i n g
M e t h o d s
Il
Co py rig hte dM ate ria l
In this concluding group of adjustable compression springs, several methods are shown in which some form of anti-friction device is used to make adjustment easier. Thrust is taken against either single or multiple steel balls, the latter including commercial ball thrust bearings. Adjustments of double spring arrangements and other unconventional methods are also illustrated. Henry Martin
Milled slots
Ad/us table nut; screwing nut info coils makes them ineffective and spring stiffer F16.18
Adjusting screw
L ong sere w with close - fit thread, no locknuf needed
Locknut
Adjusting screw
Locknut
Frame
'Hardened screw end
Guard cast integral with housing
Lock/hq key
Hardened disk
Springy centering FIG.16 plug
rlemi; spherical seat
Spring centering cone
F1G.17
Two springs to avoid cocking
Washer Adjusting nut
Swinging/ever Spring-centering bushing
Actuated, member
VWbJp -coredslot allows for angular displacement
Eyeboit turned down at end
FIG.22
Spring center
Drilled recess for baft
FIG.19
Insert washer here for easy turning
Peen or
FIG.21
spin
F l G. 23
Frame
Flanged adjusting FIG.20
nut 1
PlVOt
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Hardened and po Hs hed spring center
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Insert cup washer here if needed
Adiustina nui *
Adjusting
Spring -cen fering s^ud
90-deg, depression
nut
Co py rig hte dM ate ria l
Pin
Double-row thrusf use outer sh/efcf if is to be exposed
Polished-steel ball
bearing, spring
Drilled for pin wrench
FIG.25
FIG.24
4 hardened polished steelbat'is
Formed spring-retaining
and
cup
Spring housing
Adjusting screw, end turned down to accornodate and space steef DCtHs
HoIio w sere w
Turnedendon adjusting screw
Guard,
Cfose-fitting sh/efd
F1G.26
In fernal- spr/ng^ housing
Miffed
s/ot
Air vents.
Locknut FIG.27
V-groove in screw Piunger
Lever
Thrust washer for spring seat
Spr/ng
Actuated member
Spring retain jnq nut
Hand nut
Stationary threadecTbushing
Adjustable-outer housing
Hoiiow-end adjusting screw
Springs wound opposite hands
Adjusting key
FIG.28
Conical spring
Cover with recess for spring seat
Conical surface on ddjusting nut
Case
F16.29
Steel bails
Hollow-spr/ng center Turned-down end of actuated Hardened- steel disk member
Case Lock nut
Combined springcentering cup and bail cage
Adjustable screw Boss projecting into counter bored ho/e saves space FIG.30
Frame
Support, if spring is long
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FIG.31
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F l a t
S p r i n g s
i n
M e c h a n i s m s
These devices all rely on a flat spring for their efficient actions, which would otherwise need more complex configurations.
Co py rig hte dM ate ria l
L. Kasper
CONSTANT FORCE is approached because of the length of this U-spring, Don't align studs or spring will fall.
Upper platen
Leaf spring
Slide
SPRING-LOADED SLIDE will always return to its original position unless it is pushed until the spring kicks out.
Copyright © 2005 by The McGraw-Hill Companies
Lower platen
INCREASINGSUPPORTAREA as the load increases on both upper and lower platens is provided by a circular spring.
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Grip springs hove preloaded tension
Knob slips
Co py rig hte dM ate ria l
Knob turns shoft
Slide
Anchor bar
Handle
Spring is normoiiy straight
FLAT-WIRE SPRAG is straight until the knob is assembled; thus tension helps the sprag to grip for one-way clutching.
EASY POSITIONING of the slide is possible when the handle pins move a grip spring out of contact with the anchor bar.
CONSTANT TENSION in the spring, and thus force required to activate slide, is (almost) provided by this single coil.
Frame
VOLUTE SPRING here lets the shaft be moved closer to the frame, thus allowing maximum axial movement.
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F l a t
S p r i n g s
F i n d
M
o
r
e
W
o
r
k
Five additional examples for the way flat springs perform important jobs in mechanical devices. L. Kasper Driven friction-disc drives gear
Co py rig hte dM ate ria l
Siide
Drive rotters (notmounted on gear)
Return spring
Spring retainers
RETURN-SPRING ensures that the operating handle of this two-direction drive will always return to the neutral position.
Spring
Spring support
INDEXING is accomplished simply, efficiently, and at low cost by the Hat-spring arrangement shown here.
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Handle in maximum position
Co py rig hte dM ate ria l
Friction drive
SPRING-MOUNTED DISK changes center position as handle is rotated to move friction drive, also acts as built-in limit stop.
Holding pins
Flat spring
Clamp lever
CUSHIONING device features rapid hi crease of spring tension because of the small pyramid angle. Rebound is minimum, too.
Copyright © 2005 by The McGraw-Hill Companies
Work
HOLD-DOWN CLAMP has flat spring as* sembled with initial twist to provide clamping force for thin material.
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P n e u m a t i c
S p r i n g
R e i n f o r c e m e n t
Robert O. Parmley, RE.
A
Co py rig hte dM ate ria l
typical pneumatic spring is basically a column of trapped air or gas which is configured within a designed chamber to utilize the pressure of said air (or gas) for the unit's spring support action. The compressibility of the confined air provides the elasticity or flexibility of the pneumatic spring. There are many designs of pneumatic springs which include: hydro-pneumatic, pneumatic spring/shock absorber, cylinder, piston, constant-volume, constant mass and bladder types. The latter, bladder type, is one of the most basic designs. This type of pneumatic spring is generally composed or rubber or plastic membranes without any integral reinforcement. See Figure 1. A cost-effective method to reinforce the bladder membrane is to utilize a steel coil spring for external support. Figure 2 illustrates the conceptual design. Proper sizing of the coil spring is necessary to avoid undue stress and pinching of the membrane during both the flexing action and rest phase.
MOUNT STUD/ AIR VALVE
COIL SPRING (CROSS-SECTO I N)
ACTION
PLAN VIEW
LOADPL
LOAD
BLADDER
BLADDER ELEVATION VIEW
MOUNT PIN
BASE MOUNT
Figure 1 Copyright © 2005 by The McGraw-Hill Companies
Figure 2 Retrieved from: www.knovel.com
MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
14
Co py rig hte dM ate ria l
CAMS
14-2 Generan tig Cam Curves 14-9 Cams & Gears Team Up in Programmed Moo tin 14-11 Spherc ial Cams: Ln ikn ig Up Shafts 14-14 Modfc iato ins & Uses for Basc i Types of Cams Nomoga rms for Paraboc il Cam wtih Radc iay l Movn ig Foo lwer 14-16
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G e n e r a t i n g
C
a
m
C u r v e s
It usually doesn't pay to design a complex cam curve if it can't be easily machined-so check these mechanisms before starting your cam design.
I
Co py rig hte dM ate ria l
Preben W. Jensen
circular groove whose center, A, is displaced a distance a from the cam-plate center, A0, or it may simply be a plate cam with a spring-loaded follower (Fig IB). Interestingly, with this cam you can easily duplicate the motion of a four-bar linkage (Fig I C ) . Rocker BBo in Fig IC, therefore, is equivalent to the motion of the swinging follower in Fig IA. The cam is machined by mounting the plate eccentrically on a lathe. The circular groove thus can be cut to close tolerances with an excellent surface finish. If the cam is to operate at low speeds you can replace the roller with an arc-formed slide. This permits the transmission of high forces. The optimum design of such "power cams" usually requires timeconsuming computations, but charts were published re-
F you have to machine a cam curve into the metal blank without using a master cam, how accurate can you expect it to be? That depends primarily on how precisely the mechanism you use can feed the cutter into the cam blank. The mechanisms described here have been carefully selected for their practicability. They can be employed directly to machine the cams, or to make master cams for producing others. The cam curves are those frequently employed in automatic-feed mechanisms and screw machines. They are the circular, constant-velocity, simple-harmonic, cycloidal, modified cycloidal, and circular-arc cam curve, presented in that order. Circular cams
This is popular among machinists because of the ease in cutting the groove. The cam (Fig IA) has a
Crank
Rocker
A
B
cam groove is easily machined on turret lathe by mounting 1load• Circular the plate eccentrically onto the truck. Plate cam in (B) with spring follower produces same output motion. Many designers are unaware that this type of cam has same output motion as four-bar linkage (C) with the indicated equivalent link lengths. Hence it's the easiest curve to pick when substituting a cam for an existing linkage.
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cently (see Editor's Note at end of article) which simplify this aspect of design. The disadvantage (or sometimes, the advantage) of the circular-arc cam is that, when traveling from one given point, its follower reaches higher speed accelerations than with other equivalent cam curves.
v=constant
Constant-velocity cams Cutter
Co py rig hte dM ate ria l
A constant-velocity cam profile can be generated by rotating the cam plate and feeding the cutter linearly, both with uniform velocity, along the path the translating roller follower will travel later (Fig 2A). In the case of a swinging follower, the tracer (cutter) point is placed on an arm equal to the length of the actual swinging roller follower, and the arm is rotated with uniform velocity (Fig 2B).
u=consfont
Simple-harmonic cams
The cam is generated by rotating it with uniform velocity and moving the cutter with a scotch yoke geared to the rotary motion of the cam. Fig 3A shows the principle for a radial translating follower; the same principle is, of course, applicable for offset translating and swinging roller follower. The gear ratios and length of the crank working in the scotch yoke control the pressure angles (the angles for the rise or return strokes). For barrel cams with harmonic motion the jig in Fig 3B can easily be set up to do the machining. Here, the barrel cam is shifted axially by means of the rotating, weight-loaded (or spring-loaded) truncated cylinder. The scotch-yoke inversion linkage (Fig 3C) replaces the gearing called for in Fig 3A. It will cut an approximate simple-harmonic motion curve when the cam has a swinging roller follower, and an exact curve when the cam has a radial or offset translating roller follower. The slotted member is fixed to the machine frame 1. Crank 2 is driven around the center 0. This causes link 4 to oscillate back and forward in simple harmonic motion. The sliding piece 5 carries the cam to be cut, and the cam is rotated around the center of 5 with uniform velocity. The length of arm 6 is made equal to the length of the swinging roller follower of the actual cam mechanism and the device adjusted so that the extreme positions of the center of 5 lie on the center line of 4, The cutter is placed in a stationary spot somewhere along the centerline of member 4. In case a radial or offset translating roller follower is used, the sliding piece 5 is fastened to 4. The deviation from simple harmonic motion when the cam has a swinging follower causes an increase in acceleration ranging from 0 to 18% (Fig 3D), which depends on the total angle of oscillation of the follower. Note that for a typical total oscillating angle of 45 deg, the increase in acceleration is about 5%,
A
2.
ated by this cam, would have zero acceleration at points C, V, and D no matter in what direction the follower is pointed. Now, if the cam is moved in the direction of CE and the direction of motion of the translating follower is lined perpendicular to CE, the acceleration of the follower in points C, V3 and D would still be zero.
Cycloidal motion
This curve is perhaps the most desirable from a designer's viewpoint because of its excellent acceleration characteristic. Luckily, this curve is comparatively easy to generate. Before selecting the mechanism it is worthwhile looking at the underlying theory of the cycloids because it is possible to generate not only cycloidal motion but a whole family of similar curves. The cycloids are based on an offset sinusoidal wave (Fig 4). Because the radii of curvatures in points C7 V, and D are infinite (the curve is "flat11 at these points), if this curve was a cam groove and moved in the direction of line CVD, a translating roller follower, actu-
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Idler
A
producing simple har3 • For monic curves: (A) Scotch yoke device feeds cutter while gearing arrangement rotates cam; (B) truncated-cylinder slider for
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cam is 2 • Constant-velocity machined by feeding the cutter and rotating the cam at constant velocity. Cutter is fed linearly (A) or circularly (B)1 depending on type of follower. Cutter.
Co py rig hte dM ate ria l
V2=constant
B
This has now become the basic cycloidal curve, and it can be considered as a sinusoidal curve of a certain amplitude (with the amplitude measured perpendicular to the straight line) superimposed on a straight (constant-velocity) line. The cycloidal is considered the best standard cam contour because of its low dynamic loads and low
B
3. Geared
4 • Layout of a cycloidal curve.
C
Miffing .cutter
Barrel com
o
input
Cutter position {stationary in spaceJ
Scotch yoke
cylindrical cam; (C) scotch-yoke inversion linkage for avoiding gearing; (D) increase in acceleration when translating follower is replaced by swinging follower.
Acceleration ratio
Tension boding
WHh deviation
Without demotion
Total angle of oscillation, deg.
Copyright © 2005 by The McGraw-Hill Companies
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D
specific slope at P. There is a growing demand for this type of modification, and a new, simple, graphic technique developed for meeting such requirements will be shown in the next issue.)
shock and vibration characteristics. One reason for these outstanding attributes is that it avoids any sudden change in acceleration during the cam cycle. But improved performances are obtainable with certain modified cycloidals.
Generating the modified cycloidals One of the few devices capable of generating the family of modified cycloidals consists of a double carriage and rack arrangement (Fig 6A). The cam blank can pivot around the spindle, which in turn is on the movable carriage /. The cutter center is stationary. If the carriage is now driven at constant speed by the lead screw, in the direction of the arrow, the steel bands 1 and 2 will also cause the cam blank to rotate. This rotation-and-translation motion to the cam will cause a spiral type of groove. For the modified cycloidals, a second motion must be imposed on the cam to compensate for the deviations from the true cycloidal. This is done by a second steel band arrangement. As carriage / moves, the bands 3 and 4 cause the eccentric to rotate. Because of the stationary frame, the slide surrounding the eccentric is actuated horizontally. This slide is part of carriage //, with the result that a sinusoidal motion is imposed on to the cam. Carriage / can be set at various angles fi to match angle /3 in Fig 5B and C. The mechanism can also be modified to cut cams with swinging followers.
Modified cycloids
Co py rig hte dM ate ria l
To get a modified cycloid, you need only change the direction and magnitude of the amplitude, while keeping the radius of curvature infinite at points C, V, and D. Comparisons are made in Fig 5 of some of the modified curves used in industry. The true cycloidal is shown in the cam diagram of A. Note that the sine amplitudes to be added to the constant-velocity line are perpendicular to the base. In the Alt modification shown in B (after Hermann Alt, German kinematician, who first analyzed it), the sine amplitudes are perpendicular to the constant-velocity line. This results in improved (lower) velocity characteristics (see D), but higher acceleration magnitudes (see E). The Wildt modified cycloidal (after Paul Wildt\ is constructed by selecting a point w which is 0.57 the distance Tt 2, and then drawing line wp through yp which is midway along OP. The base of the sine curve is then constructed perpendicular to yw. This modification results in a maximum acceleration of 5.88 hi T2, whereas the standard cycloidal curve has a maximum acceleration of 6.28 hiT2. This is a 6.8% reduction in acceleration, (It's quite a trick to construct a cycloidal curve to go through a particular point P—where P may be anywhere within the limits of the box in C—and with a
Circular-arc cams Although in recent years it has become the custom to turn to the cycloidal and other similar curves even when speeds are low, there are many purposes for which
Dwelt
True cycloid WIL DT modified cycloid ALT modified cycloid.
Projection of sine curve
A
Sine curve
True cycloid WILDT ALT
Sine curve
B
C
Com rofotion Sine curve
D
Com rotation
Acceleration
Dwell
Velocity
Rise*
Family of cycloidal curves: • (A) standard cycloidal motion; (B) modification according to H. Alt; (C) modification according to P. Wildt; (D) comparison of velocity characteristics; (E) comparison of acceleration curves.
5
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E
Co py rig hte dM ate ria l
circular-arc cams suffice. Such cams are composed of circular arcs, or circular arcs and straight lines. For comparatively small cams the cutting technique illustrated in Fig 7 produces good accuracy. Assume that the contour is composed of circular arc J-2 with center at 0%, arc 3-4 with center at Os, arc 4-5 with center at O1, arc 5-6 with center at O^ arc 7-1 with center at O1, and the straight lines 2-3 and 6-7. The method involves a combination of drilling, lathe turning, and template filing. First, small holes about 0.1 in diameter are drilled at O1, O3, and Oj,, then a hole is drilled with the center at O2 and radius of ru. Next the cam is fixed in a turret lathe with the center of rotation at Ou and the steel plate is cut until it has a diameter of 2r5. This takes care of the larger convex radius. The straight lines 6-7 and 2-3 are now milled on a milling machine. Finally, for the smaller convex arcs, hardened pieces are turned with radii ru r3, and r4. One such piece is shown in Fig 7B. The templates have hubs which fit into the drilled holes at O1, O3, and 0*. Now the arc 7-1, 3-4, and 5-6 are filed, using the hardened templates as a guide. Final operation is to drill the enlarged hole at O1 to a size that a hub can be fastened to the cam. This method is frequently better than copying from a drawing or filing the scallops away from a cam where a great number of points have been calculated to determine the cam profile.
for machining cir7r •areTechnique cular-arc cams. Radaii r and turned on lathe; hardened s
5
templates added to n, rs, and r* for facilitating hand filing.
Template
Compensating for dwells One disadvantage with the previous generating devices is that, with the exception of the circular cam, they cannot include a dwell period within the rise-and-fall cam
Cam blank
Lead screw.
Carriage II
Steel band 1,
Combined motion
Sfee/ band 3
Gear (input)-
Output
Cutter
Steel bond 2
^Eccentric
Racks
Scotch yoke
B Stationary frame Mechanisms for generating • (A) modified cycloidal curves, and (B) basic cycloidal curves.
6
Slot for fastening bands I and 2
Angle fi in Fig. 5 A
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cycle. The mechanisms must be disengaged at the end of rise and the cam rotated in the exact number of degrees to where the fall cycle begins. This increases the inaccuracies and slows down production. There are two devices, however, that permit automatic machining through a specific dwell period: the double-geneva drive and the double eccentric mechanism.
360 deg (one cam cycle)
A
Desired output
Co py rig hte dM ate ria l
Double-genevas with differential Assume that the desired output contains dwells (of specific duration) at both the rise and fall portions, as shown in Fig 8A. The output of a geneva that is being rotated clockwise will produce an intermittent motion similar to the one shown in Fig 8B—:a rise-dwell-risedwell . . . etc, motion. These rise portions are distorted simple-harmonic curves, but are sufficiently close to the pure harmonic to warrant use in many applications. If the motion of another geneva, rotating counterclockwise as shown in (C), is added to that of the clockwise geneva by means of a differential (D), then the sum will be the desired output shown in (A). The dwell period of this mechanism is varied by shifting the relative position between the two input cranks of the genevas. The mechanical arrangement of the mechanism is shown in Fig 8D. The two driving shafts are driven by gearing (not shown). Input from the four-star geneva to the differential is through shaft 3; input from the eight-station geneva is through the spider. The output from the differential, which adds the two inputs, is through shaft 4. The actual device is shown in Fig 8E. The cutter is fixed in space. Output is from the gear segment which rides on a fixed rack. The cam is driven by the motor which also drives the enclosed genevas. Thus, the entire device reciprocates back and forth on the slide to feed the cam properly into the cutter.
B
F o u r - s t a t i o n geneva
C
E i g h t - s t a t i o n geneva genevas with differ8 • Double ential for obtaining long
dwells. Desired output characteristic (A) of cam is obtained by adding the motion (B) of a fourstation geneva to that of (C) eight-station geneva. The mechanical arrangement of genevas with a differential is shown in (D); actual device is shown in (E). A wide variety of output dwells (F) are obtained by varying the angle between the driving cranks of the genevas.
Genevas driven by couplers When a geneva is driven by a constant-speed crank, as shown in Fig 8D, it has a sudden change in acceleration at the beginning and end of the indexing cycle (as the crank enters or leaves a slot). These abrupt changes can be avoided by employing a four-bar linkage with coupler in place of the crank. The motion of the coupler point C (Fig 9) permits smooth entry into the geneva slot.
Double eccentric drive This is another device for automatically cutting cams with dwells. Rotation of crank A (Fig 10) imparts an oscillating motion to the rocker C with a prolonged dwell at both extreme positions. The cam, mounted on the rocker, is rotated by means of the chain drive and thus is fed into the cutter with the proper motion. During the dwells of the rocker, for example, a dwell is cut into the cam.
Coupler point
B
Input
*o
Four-dor linkage
B0
A
Geneva (output) Four-bar coupler mechanism for re• placing the cranks in genevas to obtain smoother acceleration characteristics.
9
Copyright © 2005 by The McGraw-Hill Companies
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input ,crank, 2 Bevet-geor Spider difierentidi
input crank, 2 Angle between arms, a a =90 deg
Output
D
Co py rig hte dM ate ria l
a=135deg
Double geneva with differential
a=WO deg
g=255deg
Geneva enclosed in housing
Cam
Fixed cutter
360deg
Output gear
Input driven by motor
F Various dwell resultants
Rack E Final mechanism
Com
Cutter
Chain
Output
Input C
B
* A Double eccentric drive for automatically cutting cams with dwells. • " • Cam is rotated and oscillated, with dwell periods at extreme ends of oscillation corresponding to desired dwell periods in cam.
Copyright © 2005 by The McGraw-Hill Companies
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C a m s i n
a n d
G e a r s
P r o g r a m m e d
T e a m
U p
M o t i o n
Pawls and ratchets are eliminated in this design, which is adaptable to the smallest or largest requirements; it provides a multitude of outputs to choose from at low cost.
Co py rig hte dM ate ria l
Theodore Simpson
A new and extremely versatile mechanism provides a programmed rotary output motion simply and inexpensively. It has been sought widely for filling, weighing, cutting, and drilling in automatic and vending machines. The mechanism, which uses overlapping gears and cams (drawing below), is the brainchild of mechanical designer Theodore Simpson of Nashua, N. H. Based on a patented concept that could be transformed into a number of configurations , PRIM (Programmed Rotary Intermittent Motion), as the mechanism is called, satisfies the need for smaller devices for instrumentation without using spring pawls or ratchets.
Output gear
It can be made small enough for a wristwatch or as large as required. Versatile output. Simpson reports the following major advantages: • Input and output motions are on a concentric axis. • Any number of output motions of varied degrees of motion or dwell time per input revolution can be provided. • Output motions and dwells are variable during several consecutive input revolutions. • Multiple units can be assembled on a single shaft to provide an almost limitless series of output motions and dwells. • The output can dwell, then snap around. How it works. The basic model
2
1
Program gear
Locking lever
Cam
3
idler
Basic intermittent-motion mechanism, at left in drawings, goes through the rotation sequence as numbered above.
Copyright © 2005 by The McGraw-Hill Companies
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space between the gear segments. The number of output revolutions does not have to be the same as the number of input revolutions. An idler of a different size would not affect the output, but a cluster idler with a matching output gear can increase or decrease the degrees of motion to meet design needs. For example, a step-down cluster with output gear to match could reduce motions to fractions of a degree, or a step-up cluster with matching output gear could increase motions to several complete output revolutions. Snap action. A second cam and a spring are used in the snap-action version (drawing below). Here, the cams have identical cutouts. One cam is fixed to the input and the other is lined up with and fixed to the program gear. Each cam has a pin in the proper position to retain a spring; the pin of the input cam extends through a slot in the program gear cam that serves the function of a stop pin. Both cams rotate with the input shaft until a tooth of the program gear engages the idler, which is locked and stops the gear. At this point, the program cam is in position to release the lock, but misalignment
of the peripheral cutouts prevents it from doing so. As the input cam continues to rotate, it increases the torque on the spring until both cam cutouts line up. This positioning unlocks the idler and output, and the built-up spring torque is suddenly released. It spins the program gear with a snap as far as the stop pin allows; this action spins the output. Although both cams are required to release the locking lever and output, the program cam alone will relock the output—a feature of convenience and efficient use. After snap action is complete and the output is relocked, the program gear and cam continue to rotate with the input cam and shaft until they are stopped again when a succeeding tooth of the segmented program gear engages the idler and starts the cycle over again.
Co py rig hte dM ate ria l
(drawing, below left) repeats the output pattern, which can be made complex, during every revolution of the input. Cutouts around the periphery of the cam give the number of motions, degrees of motion, and dwell times desired. Tooth sectors in the program gear match the cam cutouts. Simpson designed the locking lever so one edge follows the cam and the other edge engages or disengages, locking or unlocking the idler gear and output. Both program gear and cam are lined up, tooth segments to cam cutouts, and fixed to the input shaft. The output gear rotates freely on the same shaft, and an idler gear meshes with both output gear and segments of the program gear. As the input shaft rotates, the teeth of the program gear engage the idler. Simultaneously, the cam releases the locking lever and allows the idler to rotate freely, thus driving the output gear. Reaching a dwell portion, the teeth of the program gear disengage from the idler, the cam kicks in the lever to lock the idler, and the output gear stops until the next programgear segment engages the idler. Dwell time is determined by the
2
Output gear
Program gear
1
Locking lever
Program cam Spring
Input cam
3
Idler
Snap-action version, with a spring and with a second cam fixed to the program gear, works as shown in numbered sequence.
Copyright © 2005 by The McGraw-Hill Companies
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S p h e r i c a l
C a m s :
L i n k i n g
U p
S h a f t s
European design is widely used abroad but little-known in the U.S. Now a German engineering professor is telling the story in this country, stirring much interest. Anthony Hannavy
motion in agricultural, textile, and printing machinery. Recently, Prof. W. Meyer zur Cappellen of the Institute of Technology, Aachen, Germany, visited the U. S. to show designers how spherical-cam mechanisms work and how to design and make them. He
and his assistant kinematician at Aachen, Dr. G. Dittrich, are in the midst of experiments with complex spherical-cam shapes and with the problems of manufacturing them. Fundamentals. Key elements of spherical-camrnechanism (above Fig. J) can be considered as being posi-
Co py rig hte dM ate ria l
roblem: to transmit motion between two shafts in a machine when, because of space limitations, the shaft axes may intersect each other. One answer is to use a spherical-cam mechanism, unfamiliar to most American designers but used in Europe to provide many types of
P
Input cam
Input cam
3
Spherical mechanism with radial follower
4 Cam mechanism with flat-faced follower
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Plane ring
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Radial roller follower shown on a sphere
Mechanism with radial roller follower shown on a sphere
Spring-loaded follower
Follower
Input cani
Input cam
1
Spherical cam mechanism with radial follower
2 Cam mechanism with rocking roller follower
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Knife edge follower
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Input cam
Cone roller
Input cam
5
Hollow-sphere cam mechanism
tioned on a sphere. The center of this sphere is the point where the axes of rotation of the input and follower cams intersect. In a typical configuration in an application (Fig. 1), the input and follower cams are shown with depth added to give them a conical roller surface. The roller is guided along the conical surface of the input cam by a rocker, or follower. A schematic view of a sphericalcam mechanism (above Fig. 2) shows how the follower will rise and fall along a linear axis. In the same type of design (Fig. 2), the follower is spring-loaded. The designer can also use a rocking roller follower (Fig. 3) that oscillates about an axis that, in turn, intersects with another shaft. These spherical-cam mechanisms using a cone roller have the same output motion characteristics as spherical-cam designs with non-rotating circular cone followers or spherically-shaped followers. The flat-faced follower in Fig. 4 rotates about an axis that is the contact face rather than the center of the plane ring. The plane ring follower corresponds to the flat-faced follower in plane kinematics. Closed-form guides. Besides having the follower contained as in Fig. 2, spherical-cam mechanisms can be designed so the cone roller on the follower is guided along the body of the input cam. For example, in Fig.
6
Mechanism with Archimedean spiral; knife-edge follower
5, the cone roller moves along a groove that has been machined on the spherical inside surface of the input cam. However, this type of guide encounters difficulties unless the guide is carefully machined. The cone roller tends to seize. Although cone rollers are recommended for better motion transfer between the input and output, there are some types of motion where their use is prohibited. For instance, to obtain the motion diagram shown in Fig. 6, a cone roller would have to roll along a surface where any change in the concave section would be limited to the diameter of the roller. Otherwise there would be a point where the output motion would be interrupted. In contrast, the use of a knife-edge follower theoretically imposes no
Copyright © 2005 by The McGraw-Hill Companies
limit on the shape of the cam. However, one disadvantage with knifeedge followers is that they, unlike cone followers, slide and hence wear faster. Manufacturing methods. Spherical cams are usually made by copying from a stencil. In turn, the camshaped tools can be copied from a stencil. Normally the cams are milled, but in special cases they are ground. Three methods for manufacture are used to make the stencils: • Electronically controlled pointby-point milling. • Guided-motion machining. • Manufacture by hand. However, this last method is not recommended, because it isn't as accurate as the other two.
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M o d i f i c a t i o n s f o r
B a s i c
a n d
T y p e s
o f
U s e s C a m s
Co py rig hte dM ate ria l
Edward Rahn
FLAT PLATE CAM—Essentially a displacement cam. With it, movement can be made from one point to another along any desired profile. Often used in place of taper attachments on lathes
dwell
harmonic motion
for form turning. Some have been built in sections up to 15 ft. long for turning the outside profile on gun barrels. Such cams can be made either on milling machines or profiling machines.
dwelt
BARREL CAM—Sometimes called a cylindrical cam. The follower moves in a direction parallel to the cam axis and lever movement is reciprocating. As with other types of cam, the base
curve can be varied to give any desired movement. Internal as well as external barrel cams are practical. A limitation: internal cams less than 11 in. in diam. are difficult to make on cam millers.
dwell
dwelt-
uniform rise
,uniform rise
iwell
WweB
harmonic curve
Roller NON-UNIFORM FACE CAM—Sometimes called a disk cam. Follower can be either a roller, hexagon or pointed bar. Profile can be derived from a straight line, modified straight line, harmonic, parabolic or non-uniform base curve. Generally, the shock imposed by a cam designed on a straight line base curve is undesirable. Follower usually is weight loaded, although spring, hydraulic or pneumatic loading is satisfactory.
BOX CAM—Gives positive movement in two directions. A profile can be based on any desired base curve, as with face cams, but a cam miller is needed to cut it; whereas with face cams, a band saw and disk grinder could conceivably be used. No spring, pneumatic or hydraulic loading is needed for the followers. This type cam requires more material than for a face cam, but is no more expensive to mill.
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l
Roller
SIDE CAM—Essentially a barrel cam having only one side. Can be designed for any type of motion, depending on requirements and speed of operation. Spring or weight loaded followers of either the pointed or roller type can be used. Either vertical or
horizontal mounting is permissible. Cutting of the profile is usually done on a shaper or a cam miller equipped with a small diameter cutter, although large cams 24 in, in diameter are made with 7-in. cutters.
t of index plate
Keyway
INDEX CAM—Within limits, such cams can be designed for any desired acceleration, deceleration and dwell period. A relatively short period for acceleration can be alloted on high speed cams
harmonic motion
such as those used on zipper-making equipment on which indexing occurs 1,200 to 1,500 times per minute. Cams of this sort can also be designed with four or more index stations.
iwell
dwell
4weh
uniform rise
Roller
Jiqrmonic motion
Rdller
Roller
DOUBLE FACE CAM—Similar to single face cam except that it provides positive straight line movement in two directions. The supporting fork for the rollers can be mounted separately or between the faces. If the fork fulcrum is extended beyond the pivot point, the cam can be used for oscillatory movement. With this cam, the return stroke on a machine can be run faster than the feed stroke. Cost is more than that for a box cam
/tormonic motion
VweIi
Roller
SINGLE-FACE CAM WITH TWO FOLLOWERS—Similar in action to a box or double face cam except flexibility is less than that for the latter type. Cam action for feed and return motions must be the same to prevent looseness of cam action. Used in place of box cams or double face cams to conserve space, and instead of single face cams to provide more positive movement for the roller followers.
Copyright © 2005 by The McGraw-Hill Companies
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N o m o g r a m w i t h
f o r
R a d i c a l l y
P a r a b o l i c M o v i n g
C a m
F o l l o w e r
Rudolph Gruenberg
The useful work transferred from the cam-shaft to the follower increases as the pressure angle decreases because the force component in the direction of the follower is proportional to the cosine of the pressure angle. Designing for maximum efficiency, therefore, involves a trial and error balance of least maximum cam pressure angle against the mechanical limitations of the cam and its adjacent components. The nomogram below reduces this to a minimum and affords a quick check of an already established design.
Co py rig hte dM ate ria l
THE DEVELOPMENT of theoretically correct cam profiles is often complex and time consuming. In applications having neither high speeds nor forces, such efforts are unwarranted. In these applications, parabolic or gravity cams are usually adequate. The efficiency of operating a cam-mechanism depends predominantly on the pressure angle. Since it is a measure of the greatest side thrust on the follower arm, the maximum pressure angle must be determined since it controls the physical dimensions of the cam.
Line H
Line *
Example: Given L =0.5, R=2.5, /5 =70 deg
Solution s
ocr ie deg
Lift L
Pivot
Max. press.
Cam angle
angle <X ,deg.
Copyright © 2005 by The McGraw-Hill Companies
Meon Radius R, in. (Radius at V2Ii)
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION 15
Co py rig hte dM ate ria l
GROMMETS, SPACERS & INSERTS A Fresh Look at Rubber Grommes t 15-2 These Spacers Are Adu jstabe l 15-4 Odd Jobs for Musho rom Bumpers 15-6 Spacers Used in Jg is & Fx itures 15-8 Falnged n I serts Stabzile Mutl-iStroke Reo ladn ig Press 15-9 Metal n I serts for Pa lstc i Parts 15-10 How to See lct Threaded n I serts 15-12 Appc ilato ins of Helical Wrie n I serts 15-15
Copyright © 2005 by The McGraw-Hill Companies
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A
F r e s h
L o o k
a t
R u b b e r
G r o m m e t s
A small component that's often neglected in the details of a design. Here are eight unusual applications.
Co py rig hte dM ate ria l
Robert O. Parmley
Rubber Grommet
Rubber Grommet
Housing
Rubber Grommet
Shaft Rope or Twine
Shaft
Rope or Twine-
Pulley for slow rotation
Handle shaft misalignment
Liquid Entry-
Delicate Panels
Fill Nozzle
Rubber GrpMMt
Rubber Grommet
Flat Washer (MeMt ;
Chamber
Seat for liquid filling
Cushioned spacers
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Guide Rod
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Wire Boil
Travel
Rubber Grommet
Beiievilfe Wasnen GfassPfote
£&ncfr
Rubber Grommet
Guide liner
Support delicate work plates
Rubber Grommet
Straight Edge of inking Ruier
Sec A-A
Action
Rubber Grommet
Metaf Flat Washer Ta Moid Collapse
Riyet\
Rubber Grammei
Stroignt Edge
Straightedge pads
Shock absorber
Copyright © 2005 by The McGraw-Hill Companies
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Housings
T h e s e
S p a c e r s
A r e
A d j u s t a b l e
Rubber, metal springs, jackscrews, pivoting bars and sliding wedges allow adjustment after assembly.
Co py rig hte dM ate ria l
Richard A. Cooper
C&pi^-espfap
WMer spacer
COMPRESSION
TUBULAR RUBBER SPACER is k»vcbst," efjfic&nf deVicFfOr space adypstment andshdcklabporptioii.] ] I I )
SPRING shouTd Tie
tside^effedtmWihefspfifigr-i
!—I h }•••
locating head, of, sdrety
pt^feif kleme.
t%£&ad&.
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KfHirfeti
"Ffotwwmr Yo ffates]
Ltick tiut
.....iloatl4ir.4as^..rcjui^¥at X [.......4 u . } .(,.. )....
Copyright © 2005 by The McGraw-Hill Companies
OPPOSITE-THREADED STMDl 4ievi^e li>r muviug i o t k ^ r i s i x a b f l i i ^ e ^ame distance >villi oiie adjustiucut. - \
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Co py rig hte dM ate ria l
-fMfer
leaf
MtAtktk
RUBBER-SUPPORTED STUD Ls attachod to the metal jrfate. Support heavy! !loads with this assembly* ^ ; >
JJE^[Sf?RiH<^e№ to prevent their digging into the bottom Jpart*Ji*hiclrixopl4^piey^jitlad|jjus^^ I
bbcm
TftWWg "SVfWW
SeA sere is
\Maxfyuni
---ifivgQifmjGHta^ justnient ivhcre torque at clamping points
IkJUi^ Jeja^i^^
_L.
Copyright © 2005 by The McGraw-Hill Companies
j&L|0l(N^ ANOL^B^Of KjS permit great] ucc«^K> in ^iitHiltitncous lateral and vcrti-
.kaLia4iwsbM^wt|.Mbi:tsi L j
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;
;: i_
O d d
J o b s
f o r
R u b b e r
M u s h r o o m
B u m p e r s
High energy absorption at low cost is the way mushroom bumpers are usually billed. But they have other uses; here are seven that are rather unconventional. Robert O. Parmley
Co py rig hte dM ate ria l
Vchcuam f^eased \ orwrfwuW 'Smptiek
C/dsedff wif&ivatt/t/m
4pr4pdhd
P/aff/c tob# i Rubber rhush/obm
Muk J...... Sieme
Bumper,
fiou^ing
'WeWo/ice
Rui^eAm^hfpom bunipeh \ \ \ hedted whenclosedJ
snttg fit vnhtfe
AiL. escdpe
.Mjf.ps#$svre.
Wkilsa/der)
Discharge ^alvehf^r tubirtg i
:
X
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I
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4 i r ) Vt
e $ s t i r c j v ^ N e {••
;
7/$rd$neB~'?y6&erji
Secfwftkf
Cl&irkopihhof
Rifbb&t^W^slkdiM kof^e^
A! "SlnTsecTfpn Rtibbhr mush room, b dmper tskugXfifJ
.MnckphsiuMt I^uric1ii^;|>r^^
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0rairi j$Iiijgst
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a
Co py rig hte dM ate ria l
Rubber mkshroom tamper
Motor
Rubber mashroorfi bumper
fpresis-Jit
Brockets
ar &№#}
-Wait
Vhomber toss
Cop
mbber W$hrQqm $u/pper
Tighte/t dpwti
Bfockef
Log screw
Chamber
Chamber plug
Cushion motor vibration
Qgmpm times..
Work wi&ce
ku^be^ 6$£*f£.?.i$ d?iin(fe
Clamp delicate parts
Copyright © 2005 by The McGraw-Hill Companies
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i n
J i g s
&
F i x t u r e s
PRESS FIT
SPACER STUD
GROOVE
SPACER STUD
WORK
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U s e d
THREADED STUD
PILOT WHEEL
S p a c e r s
Copyright © 2005 by The McGraw-Hill Companies
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F l a n g e d
I n s e r t s
R e l o a d i n g
S t a b i l i z e
M u l t i - S t r o k e
P r e s s
Co py rig hte dM ate ria l
E. E. Lawrence, Inventor Robert O. Parmley, Draftsman
Flanged Insert
Flanged Insert
Flanged Insert
Copyright © 2005 by The McGraw-Hill Companies
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M e t a l
I n s e r t s
f o r
P l a s t i c
P a r t s
Co py rig hte dM ate ria l
Plastics are increasingly used in automobiles and appliances and thus a major company compiled these data.
Molded parts should be designed around any inserts that are required. This work is done after the type of compound is selected. Inserts are used for two basic reasons: 1. To add strength to the plastic part or to control shrinkage. Sometimes the purpose is to be decorative or to avoid injuries. 2. To provide an attachment means for the conductance of heat or electricity. Special means of retention are not necessary for inserts not subject to movement with relation to the molding material. Inserts of round bar stock, coarse diamond knurled and grooved, provide the strongest anchorage under torque and tension. A large single groove, as in Fig. 1, is better than two or more grooves and smaller knurled areas.
ONE END BURIED
Inserts secured by press or shrink fits
BOTH ENDS PROTRUDING
Inserts can be secured in the plastic by a press fit or shrink fit. Both methods rely upon shrinkage of the plastic, which is greatest immediately after removal from the mold. The part should be made so that the required tightness is obtained after the plastic has cooled and shrinkage has occurred. The amount of interference required depends on the size, rigidity and stresses to be encountered in service. The hole to receive the mating part should be round and countersunk. In addition, the mating part should be chamfered and filleted to facilitate proper assembly and to eliminate stress concentration.
»03 Min chamfe r
.50D Min
MALE
.03 Min
Standard nut
.25D Min 1. Depth of knurling should be about 0.001 in. and a single groove is best
FEMALE 2. Round knurled parts are common inserts
Reprinted with permission from American Machinist, A Penton Media Publication Copyright © 2005 by The McGraw-Hill Companies
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Punched hoLes
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Lanced hole
,75 D Min
.12 Min
.12 Min
Ribs
BeLow boss level
Not recommended
Preferred
Recommended minimum space between inserts
Extend insert beLow boss and reinforce with ribs Hexagonal, insert
Circular boss
Metal mold member
.75 D Min
Provide circular bosses around noncircular inserts
Let internally threaded inserts enter the machine mold to prevent fLash from getting into thread.
3- Sheet metal and special inserts, as well as knurled inserts, are used to provide connections and closures
Copyright © 2005 by The McGraw-Hill Companies
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H o w
t o
S e l e c t
T h r e a d e d
I n s e r t s
Why use threaded inserts? What types are available? What factors govern their selection? How do you determine whether a particular insert meets the given strength requirements and which one is most economical?
Co py rig hte dM ate ria l
S. H. Davison
\Nhen the design calls for lightweight materials like aluminum, magnesium and plastics, threaded holes become a problem because of the low shear strength of these materials. To bolt such components to other machine parts, the threaded holes must be quite deep to develop the required pull-out strength, or they must have a coarse thread to increase shear area. Further complications arise when the components require frequent disassembly for overhaul or repair; this may give excessive thread wear that will prevent satisfactory thread engagement with the bolt, particularly for high-strength bolts in the fine-thread series; and the depth of engagement needed will require a part so thick as to nullify the lightweight advantage of the material. To overcome these problems, thread inserts of highstrength material are often used. Inserts available
Three main types of inserts are available: 1. Wire thread inserts are precision coils of diamondshape stainless steel wire. They line a tapped hole and present a strong, accurate, standard internal thread for
the bolt or stud. The OD on these inserts is from 11 to 30% greater than the OD of the internal thread—the lower limit is normally used on the fine-thread inserts specified in aircraft engines. The pull-out strength of wire thread insert depends on shear area of its OD thread. 2. Solid self-tapping inserts require only a drilled hole and counterbore in the part, and are made in two basic forms. (1) A solid self-tapping, self-locking bushing has a 60% external thread approximating the American National form with a uniform OD extending to the first 2 to 2i threads. These leading threads are slightly truncated to provide the cutting action necessary for self-tapping. Chips flow out through the side hole drilled in the insert wall at the truncated lead threads. (2) A second type has lead threads similar to the pilot threads of a standard tap. These threads progressively flow into truncated threads extending the entire length of the insert-^with the exception of the last three threads, which are standard. In both types, two or three angular slots, depending on the particular design, provide the cutting action for selftapping. 3. Solid bushings for pre-tapped holes are also made in
A
WIRE THREAD INSERTS made of diamond-shape stainless steel wire. Pull-out strength of material depends on ratio of internal to external thread shear area.
B
SOLID SELF-TAPPING INSERTS are of two types—(A) chips are removed through the side hole; or (B) with truncated lead threads and two or three angular slots which provide cutting action.
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C
Co py rig hte dM ate ria l
A
B
SOLID INSERTS FOR PRETAPPED HOLES have many variations. Among the most popular are: (A) modified external threads for interference and locking action; (B) two-piece unit with key ring for locking action; (C) integral keys give locking action; (D) expandable collar with external serrations.
D
two general types. The first uses modified external threads that form an interference with the parent material, and provide locking action. The second type has many variations, but is characterized by standard external and internal threads, with various types of pins or keys to lock the bushing to the parent material. Some of the most widely used variations are: A two-piece insert with a locking ring and two keys fits into mating grooves in upper external threads. The ring is pressed into place after the insert is screwed into tapped hole; it cuts through enough threads of parent material to provide a positive lock. A counterbore in the tapped hole is required for the ring, but assembly and replacement can be made with standard tools. Another solid bushing insert has two integral keys which act as a broaching tool when insert is installed flush with the parent material. Locking pins are pressed into the base of the tapped hole through the grooves in the external thread. Still another, a solid bushing, has standard internal and external threads and an expandable upper collar with serrations in the outer surface to lock the insert in the parent material. Factors that affect selection These factors must be considered in selecting the best type: • Shear strength of parent material
• • • • •
Operating temperature Load requirement Vibratory loads Assembly tooling-serviceability and ease of installation Relative cost
Shear strength of parent material below 40,000 psi generally calls for threaded inserts. This includes most of the aluminum alloys, all magnesium alloys and plastic materials. But other factors must be considered. High operating temperature effects the shear strength by reducing strength of the parent material; an insert with a larger shear area may be required. Bolt loading frequently makes it necessary to use threaded inserts. For example, if the full pull-out strength of a 125,000-psi bolt is required, it is probable that the parent material will need a threaded insert to increase the shear area and thus reduce the effective shear stress. Vibratory loads may reduce bolt preload, and require a threaded insert to increase the effective shear area. Or vibration may cause creep, galling, and excessive wear, and inserts with both external and internal thread-locking features will be needed. The pullout capacity of an insert is a function of projected shear area, and should equal the tensile strength of the bolt. This means pull-out strength should be greater than torque-applied tensile strength of the bolt. In wire thread inserts the projected shear area per coil
Copyright © 2005 by The McGraw-Hill Companies
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No. of Assy. Operations
COST OF PART is price quoted for lots of 1000.
NUMBER
OF ASSEMBLY
TOOL COST for each type is based on manufacturer's prices for tooling a standard tapping head.
OPERA-
TIONS covers complete installation of an insert, including drill, counterbore, tap, ream, install and reinspect.
Ratio of InternalD Dia. to Length ~ /j_
Ease oi Assy
Tool Cost
Co py rig hte dM ate ria l
Cost of Part
RELATIVE EVALUATION—5 TYPES OF THREAD INSERTS (A—self-tapping insert; 8—wire thread insert; C—solid hushing for pre-tapped holes; D—solid bushings for pre-tapped holes and external interference threads; E—self-tapping insert)
Effective Shear Area, sq in.
A USEFUL RELATION is effective shear area to DfL ratio. It determines required insert length or pull-out strength. Solid curves are for self-tapping inserts; dotted curves for wire thread inserts.
is relatively small; only way to increase the total projected shear area is to increase the number of coils. On the other hand, in solid and self-tapping inserts the projected shear area can be increased by a larger OD as well as by more threads, while maintaining the same bolt diameter. One way to determine adequacy of pull-out capacity is
EASE OF ASSEMBLY is a qualitative evaluation.
to plot the ratio of the internal diameter vs insert length as a function of the effective shear area developed in the parent material. The accompanying curves for three sizes of self-tapping and wire thread inserts were derived from tests in which the insert was pulled out of the parent material. Similar curves could be developed to determine the length needed for any other type of insert. For example, assume that a £-28 bolt with an ultimate strength of 5000 Ib is to be used in a material with a shear strength of 2O7OOO psi. The required shear area is 5000 lb/20,000 psi = 0.25 sq in. From the accompanying curves, the D/L ratio is 0.57; insert length, L = 0.25/0.57 = 0,438 in. Similar calculations, using the same curves, can determine whether length of the insert is sufficient to give a required amount of creep resistance: The creep strength of the parent material is substituted for shear strength in the above calculation. Also, if the insert length is limited, these calculations will give the available pull-out strength, which will vary with shear area of the insert. This analysis can be used to determine either the required length or pull-out strength, and from this, the thickness of the parent material for minimum weight and maximum economy. Solid threaded bushings often permit using a shorter bolt than for the wire thread insert with limited shear area. With a large number of fasteners in an assembly, weight saving in reduction of parent material is much greater than the small extra weight added by the solid insert. Other important factors in selecting inserts are assembly tooling, serviceability, relative cost, and ease of installation. These factors have been evaluated in the bar charts prepared by W. Moskowitz of GE's Missile and Space Vehicle Dept, Philadelphia. Data are for five types using 10-32 internal threads. Part of this information is based on estimates of the operating personnel concerning the number of assembly operations, tolerances required during installation, and relative ease of installation.
Copyright © 2005 by The McGraw-Hill Companies
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A p p l i c a t i o n s
o f
H e l i c a l
W i r e
I n s e r t s
Paul E. Wolfe
Screw
Connector
Co py rig hte dM ate ria l
Steel bolt
Insert.
Magnesium
Fig.1
Lead core Insert Fig. 3
Acrylic block
Insert
Soldered lead
Fig.2
as a thread reinforcement. Unit is threaded into plastic and tang is bent to form soldering lug.
Fig. 1—Galvanic action between steel bolt and magnesium part, (Left), attacks thread causing part failure. Stainless steel insert, (Right), reduces galvanic action to a negligible amount while strengthening threads.
Fig. 3—Direct connection of grinding wheel onto a threaded shaft by using a wire insert. Washers and nut are not required thus simplifying assembly.
Fig, 2—Insert used as an electrical connection as well
Insert and cop screw assembly
Nut and bolt assembly
tnsert
Grinding wheel
Plastic sheet
Leveling screw
Fig.8 Ball and socket joint
Plywood
Screw
Footplate
(nsert Fig.10
Fig.9
Fig. 8—Wear and backlash can be reduced on adjusting threads. Clamping strength is not needed but intermittent thread travel makes reinforcement desirable*
floors and walls. Access to opposite face of the wood is not a factor nor are joists and other obstructions.
Fig. 9—Combination of inserts and capscrews permits installation of machinery and other equipment on wood
Fig. 10—Plastic-to-wood connector. Repeated assembly and disassembly does not affect protected threads in wood or plastic parts.
Fig.15
insert
Tank
Fig,14
Stud Insert assembly Pipe plug
Fig. 14—Seizure and corrosion of pipe threads on compression, fuel and lubricant tanks, pipe lines, fittings, pumps and boilers are prevented by using an insert. Fig. 15—Stud (Left) transfers thread wear from the tapped hole and into the expendable threads on the stud and nut. Interference fit in the tapped hole is
tnsert
Internal Cop screwExternal and insert Fig.16
mandatory. Insert (Right) prevents wear and makes stud unnecessary. Lower cost cap screw can be used. Fig. 16—Thread series can be changed from special to standard, from fine to coarse or vice versa, or corrected in case of a production error by redrilling and retapping. Inserts giving desired, thread are then used*
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Co py rig hte dM ate ria l
Pulley,
Open-ended 'retaining plug
Valve
Phenolic port
Insert
Insert
Insert*
Set screw
Aluminum block Preassemb/ed cylinder head and liner
Fig.7
Fig.6
Fig. 5
Fig.4
Pressure cylinder
Insert molded-in
Fig. 4—Loosening of the set screw by vibration is reduced by using an insert. As pulley is a soft metal die casting set screw tightening often stripped threads*
Pig. 6—Phenolic part insert forms strong thread without tapping and drilling. Insert is resilient, does not crack phenolic or set up local stress concentrations.
Fig. 5—Insert withstands combustion thrust of diesel cylinder. It prevents heat seizure and scale on threaded plug making cylinder replacement and servicing easy.
Fig. 7*—Enlargement of taper pipe threads in necks of pressure vessels, caused by frequent inspection and interchange of fittings, can be minimized.
Spark p/ug
Pump housing
Engme head
insert
insert
Pipe
Fig.11
fitting
Fig. 11—Threads are protected from stripping in new aluminum engine heads by inserts. Also can be used to repair stripped spark plug holes in engine heads.
Fig. 12—Insert prevents pipe fittings from peeling chips out of tapped aluminum threads. Introduction of
Shaft
Small inserts setscrews
Fig.13
Fig.12
Large insert
Setscrews
Adjustment threads
Plastic insulating block
chips into the lines could cause a malfunction. Fig. 13—Center insert serves as brakeband to lock adjustable bushing. Small inserts keep set screws from stripping plastic when tightened. Also, adjustment threads can not be marred by end of set screw.
Bearing
\$oft ^material
Standard nutt bolt and washer assembly
Insert
Fig. 17
Fig. 17—Assembly weight may be reduced. Left view shows the standard method of attaching front and mid frame of a compressor, Lockwire is used after assembly is completed. Right view is new method resulting in weight and space economies, Hg. 18—Assembly of a shaft through a bearing is sim-
Fig.13
Insert over shaft cut threads
Fig.19
plified by adding external insert over cut shaft threads. Machining the full shaft length is also unnecessary. Fig. 19—Square tang insert—called screw lock—automatically locks the screw so that lock washers, nuts or wires are unnecessary. Insert locks itself into parent material without need for pins, rings, or staking.
Copyright © 2005 by The McGraw-Hill Companies
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
16
Co py rig hte dM ate ria l
WASHERS
d Ieas for Flat Washers Versate li Flat Washers Jobs for Flat Rubber Washers Take Anoh ter Look at Serated Washers Dsihed Washers Are Versate li Componens t Desg in Probelms Sov led wtih Belevile Sprn ig Washers Creatv ie d Ieas for Cupped Washers SEM Appc ilato ins SEM Standards Tabe ls
Copyright © 2005 by The McGraw-Hill Companies
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16-2 16-4 16-6 16-8
16-10 16-12 16-14 16-16 16-17
I d e a s
f o r
F l a t
W a s h e r s
You can do more with washers than you may think. Here are 10 ideas that may save the day next time you need a simple, quick, inexpensive design.
Co py rig hte dM ate ria l
Robert O. Parmley
Bolt
Flat washers (loose fit on shaft}
Belleville spring
Belt
loosely fitted to the shaft separates them.
Movement
Stem-
Pin
90deg approx
Hole dla
Need to hold odd-shaped parts? A flat washer and Belleville spring make a simple anchor.
Are your belts overlapping? A flat washer,
Rod,
Flat washer
Fiat washers
Float
Bent flat washer
End view
Rod'
Flat washer Base,
Liquid level (variable}
FlQQf travel
Drive
Press fit or weld
pin
How about a rod support? A bent washer permits
Got a weight problem? Adding or subtracting
some rocking; if welded, the support is stable.
flat washers can easily control float action.
Copyright © 2005 by The McGraw-Hill Companies
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(Add axle rod for fuming) Fiat washer Mount base
Pulley
Fiat washers
Concrete
Co py rig hte dM ate ria l
Shaft
Height adjustment Anchor bolt
Twine'
How about some simple flanges? Here the washers guide the twine and keep it under control.
Flat washers
Rod
Pin
Does your floor tilt? Stacked washers can level machines, or give a stable height adjustment.
Rotating index
Arm
Axle
Machine bolt
Fiat •washer
Need some wheels? Here flat washer is the wheel. A rubber disk quiets the assembly.
Flat washer
Shaft
.Flat washer
Lever
Lock
Base
Rubber disk
Fiat washer
Loosen
Here's a simple lock. A machine bolt, a washer, and a wing or lever nut make a strong clamp.
Rod*
Post Roller
Tube
Flat washer
Base
Flat PIn washer Washer Tubing
Want to avoid machining? Washers can make anchors, stop shoulders, even reduce tubing ID.
Copyright © 2005 by The McGraw-Hill Companies
Need a piston in a hurry? For light service, tube, rod, and washer will be adequate.
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V e r s a t i l e c a n
b e
u s e d
F l a t in
a
W a s h e r s :
v a r i e t y
o f
u n u s u a l
a p p l i c a t i o n s
Robert O. Parmley
Support a shaft
Co py rig hte dM ate ria l
Stiffen machine mount Machine screw
Machine base
Shaft or round stock
Flat washer
Flat washer
Cut square and weld
Rubber grommet
Flat washer
Stabilize a point
Slot
Folded flat washer
Spot weld (optional)
Channel
Point
Guide wire or tubing
Act as a valve seat Plastic ball
Weld
Bent washer
Flat washer Wire or tubing Adhesive bond
Tube
Flat washer
Sleeve Vacuum
Copyright © 2005 by The McGraw-Hill Companies
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Washers are usually thought of as bearing surfaces placed under bolt heads. But they can be used in a variety of ways that could simplify a design or be an immediate fix until a designed part is available.
Reinforce a roller
Co py rig hte dM ate ria l
Act as a pulley flange
Rolling bushing
Axle
Shoulder
Flat washer
Rubber roller
Jam nut
Flat washer
Form a pulley
Crimp tubing
Pulley bracket
Flat washer
Form a shock absorber Anchor bolt'
Anchor nut
Machine mount
Flat washers (5 large, 4 small) Cable
Metal flat washer
Rubber flat washer
Floor grade
Act as a bearing surface Fiberglass housing
Flat washers
Lock washer Plastic shell
Copyright © 2005 by The McGraw-Hill Companies
Cap screw
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J o b s
f o r
F l a t
R u b b e r
W a s h e r s
Rubber washers are more versatile than you think. Here are some odd jobs they can do that may make your next design job easier.
Co py rig hte dM ate ria l
Robert O. Parmley
Me/of washers for spacers and strength. Rubber flat washersM
,Frame
Mount leg
Adhesive bond Steel bo!!'
Rubber flat washers
Base
Impact a b s o r p t i o n idler roller
Compression
mount
P
Post
Valve stem
Rubber T flat washer •
Rubber flat washers
Concrete
Pipe sleeve
Metal disks P
Heavy shock load s u p p o r t
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Cylinder valve
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Cylinder wall ; ;
Tube crimped at end
Rubber fiat washers'
Co py rig hte dM ate ria l
Metal fiat washer at end
Step roller
Cylinder
Plug
Rubber fioi washer
Hose
Vacuum
Bali
Hose bib (connection)-
Adhesive bond
Adhesive bond
Rubber ftof washer
TiQstic chamber
Hose bib retainer
Compression ball seat
Connection
Action arc
Stem
Protects stem
Rubber flat washer, (press fit)
insulated wires
Rubber flat washers slide on wire, connect, then slip into position
Optional
Base
Boll -stem pivot
Protective bumper
Copyright © 2005 by The McGraw-Hill Companies
Expansion isolator
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T a k e a t
A n o t h e r
S e r r a t e d
L o o k W a s h e r s
They're a stock item and come in a variety of sizes. With a little thought they can do a variety of jobs. Here are just eight.
Co py rig hte dM ate ria l
Robert O. Parmley
S$f?tyteU... wGsher \
P^ Spring
ok JKreSd
.Hkusbu.
Waff
BW
WoW
kosher.
•'ifpffT
Stajprot^iojiof bolts or pins
I|in1er|g4a*i
SpctiLmM
ft
Ser'rafei Rashers iadd-for
SecJA4A
Simple gear f6rl!gftt^piili4atioris
Copyright © 2005 by The McGraw-Hill Companies
$ermtk£ kaSe/\
^
#nferwiv^d|wiretwtstt
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iimfrhiTFmi^s'
belleville Wosher
shaff
jam nut
Co py rig hte dM ate ria l
Serrated washers
vary washers for width
Bead chain
Gear or sprocket for bead chain
indexing
Retaining ring
shaff
link chain
Serrated washer
Paper or cardboard
Serrated washers
vary number for Width
Link chain sprockets
Serrated washer Solder
sheet
Material or paper drive or feeder
Rods
Maunf
hole
End mountihg for simple tumbler
Copyright © 2005 by The McGraw-Hill Companies
feed
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D i s h e d
W a s h e r s
A r e
V e r s a t i l e
C o m p o n e n t s
Let these ideas spur your own design creativity. Sometimes commercial Belleville washers will suit; other wise you can easily dish your own. Robert O. Parmley
Load
Dished washers
Jam nut
Aligning bolt
Co py rig hte dM ate ria l
Mounting plate
Shaft
Lock washer
WorApiece
Belleville spring washer (add or subtract) for height Base
Add rubber between WGshers for grip power
HEIGHT ADJUSTMENT
GUIDE WHEEL
To remove pin
Shaft
Washer
Washers
Optional weld-
Housing surface
L ocA washer
Cap screw
Brash (steel wool or wood fiber)
EASY PIN REMOVAL
BRUSH RETAINER
Load
Retaining ring
Mount plcte
Recess
Stem
Voive seat
Weld
Belleville washers
Pin
Washer Base COIL SPRING STABILIZER
Copyright © 2005 by The McGraw-Hill Companies
SIMPLE VALVE
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Pin
Washers
Shoft
Workpiece
V be If Shaft
A
Co py rig hte dM ate ria l
A
Section A-A
Washer
Workpiece
\ Add holes and bolts here for non-slipping
Dished washers
(End view of alternate, non-slip orrongement)
Base
ALIGNING BUTTONS will rotate if holding screw is shouldered
V-BELT PULLEY
Rubber surface adhesive. tope on bevels
Shouldered plastic stem
Alternate: Protect corners and surface of delicate materials Lock washer Cap screw Housing surface
Washers-
Shaft
Washer
Washer
END AND CORNER PROTECTION
Tubing,
SIMPLE BEVEL DRIVE
Washer
Belleville spring washers
Shafts
Enlarged view
Rivet over^
Wood, rubber or plastic spool
Jom nuts
FLARED SPOOL-FLANGES
Copyright © 2005 by The McGraw-Hill Companies
Work area
CORRUGATING ROLLERS FOR PAPER OR CARDBOARD
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D e s i g n
P r o b l e m s
S p r i n g
W a s h e r s
S o l v e d
w i t h
B e l l e v i l l e
Robert O. Parmley
Pulley assembly
Co py rig hte dM ate ria l
Retain tapered coil spring Veebelt (sectioned)
Shaft
Chamber
-Coil spring (tapered)
Belleville spring disc
Jam nut (2)
Lock washer (2)
Knurled adjustment sleeve
Belleville spring discs (sectioned)
Stem
Mounting spring stabilizer Force
Force
(Nut and washer optional)
Grommet seat
Belleville spring discs
Coil spring
Concrete floor
Delicate panel
Rubber grommet
Anchor bolt
Copyright © 2005 by The McGraw-Hill Companies
Belleville spring disc •
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Bench
Belleville springs are a versatile component that offer a wide range of applications. There are many places where these components can be used and their availability as a stock item should be considered when confronted with a design problem that requires a fast solution.
Secure anchor bolt
Co py rig hte dM ate ria l
Clamp fixture spring
Anchor bolt
Holding pad
Optional •floor height
Concrete floor
Sleeve
Belie.vilie spring disc
Work
Lock retainer
Compression sleeve
Belleville spring disc
Flat washer (4 required) -
Belleville spring disc (4 required)
Door
Lock mechanism
Machine leg spring mounts
Leg
Cap screw
Belleville spring discs
Cap screw
Floor
Believitle spring disc Anchor bolt A
B
Copyright © 2005 by The McGraw-Hill Companies
C
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C r e a t i v e
I d e a s
f o r
C u p p e d
W a s h e r s
A standard off-the-shelf item with more uses than many ever considered.
Co py rig hte dM ate ria l
Robert O. Parmley
Pipe
Weld
Shaft
Rod
pupped washers (sectioned)
Internal
Pipe
Cupped washer (drive fit)
Weld or solder
End
Simple step pulley
Chamber wall
Rod aligner and pipe-end bearing
Rod
Plastic tubing (removable)
Cylinder waif
Cupped washer (sectioned)
Hand press fit
Cupped washer (sectioned) Adhesive bond Air vent hole Solder Tubing connector
Copyright © 2005 by The McGraw-Hill Companies
Cupped washer (press fit or weld)
Weld
Simple piston f o r cylinder
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Nut-
Press plote
Coil spring Cupped woshers (sectioned)
Co py rig hte dM ate ria l
Pin
Coil spring stabilizer and compression brake
Cupped wosher
Concrete floor
Seated
Cupped woshers
Cupped woshers
Wooden leg
Pulley
Posts
Shaft-
Cupped washer
Cupped washer•
Solder
Roller
Base
Snap ring
Snap rings
Simple pulley and roller
Inverted
Post shoe
Post anchors and supports
Wall
Cupped woshers (sectioned)
Toggle switch
Plastic stem
Cupped washer
Toggle switch housing
Copyright © 2005 by The McGraw-Hill Companies
Protection for step shoulders
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S E M
A p p l i c a t i o n s
N. Dale Long
mercial requirements usually vary—depending upon either the designer's decision or product-cost restrictions. For good quality and reliable service, however, the fastening methods shown here can be depended on to pay off.
Co py rig hte dM ate ria l
W hen a split lockwasher is called for in a screw fastening, a flat washer is invariably necessary. The ways of assembling them illustrated below are strict requirements in military specifications—especially for electronic equipment. Com-
ASSEMBLY OF FLAT WASHERS AND SPLIT LOCK WASHIRS
Flat washers shouSd be placed between . . .
1 Metal surface, whether finished or not, and locking washer
Flat washer Lock washer
Nonmetal material
2 Nonmetal surface and locking washer
Flat washer
Fiat washer
Nonmetal material
3 Screw head and nonmeta! surface
Fiat washer
Metal 0.032-in. or less thick
Fiat washer
4 Screw head and metal that is 0.032 in. or less thick
Flat washer
5 Screw head and enlarged or elongated clearance hole
Flat washer
6 Locking washer and enlarged or elongated clearance hole Flat washer
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
S E M
S t a n d a r d
T a b l e s indentation optional
Pan Head Machine Screw
Fillister Head Type D Tapping Screw
Hex Washer Head Type T Tapping Screw
Hex Head [Note (Dj Type F Tapping Screw
Hex Cap Screw
Co py rig hte dM ate ria l
Representative Examples of Helical Spring Lock Washer Sems
Nomn i al Szi e [Note (2)] or Basci Screw Da i meter 2 0.0860 0.0990 3 0.1120 4 0.1250 5 0.1380 6 0.1640 8 0.1900 10 0.2160 12 0.2500 0.3125 3 0.3750 Z3 0.4375 0.5000 V2
DIMENSIONS OF HELICAL SPRING LOCK WASHERS FOR SEMS WITH MACHINE AND TAPPING SCREWS HAVING MACHINE SCREW THREAD DIAMETER-PITCH COMBINATIONS Pan Head Screw Filister Head Screw Hex Head Screw [Noted}] Hex Washer Head Screw Washer Washer Washer Washer Section Section Section Section Washer Washer Washer Washer Washer Thick- Outsd Thick- Outside ie Thick- Outsd ie ie Inside Thick- Outsd i meter i meter Width ness Da i meter Width ness Da Da i meter Width ness Da i meter Width ness Da
Max. 0.080 0.091 0.106 0.118 0.129 0.155 0.179 0.203 0.238 0.298 0.361 0.420 0.482
Min. 0.075 0.086 0.101 0.113 0.124 0.149 0.173 0.196 0.230 0.290 0.353 0.411 0.473
Min. Min. Max. 0.035 0.020 0.156 0.040 0.025 0.178 0.047 0.031 0.208 0.047 0.031 0.220 0.062 0.034 0.261 0.078 0.031 0.319 0.093 0.047 0.373 0.109 0.062 0.429 0.125 0.062 0.496 0.156 0.078 0.618 0.171 0.093 0.711
Min. 0.145 0.166 0.195 0.207 0.248 0.305 0.359 0.414 0.480 0.602 0.695
Min. 0.030 0.035 0.035 0.035 0.047 0.047 0.055 0.062 0.077 0.109 0.125
Min. 0.020 0.020 0.020 0.020 0.031 0.031 0.040 0.047 0.063 0.062 0.062
Max. 0.146 0.168 0.184 0.196 0.231 0.257 0.297 0.335 0.400 0.524 0.619
Min. 0.135 0.156 0.171 0.183 0.218 0.243 0.283 0.320 0.384 0.508 0.603
Min. 0.030 0.035 0.040 0.047 0.047 0.055 0.062 0.070 0.109 0.125 0.141 0.156 0.171
Min. 0.020 0.020 0.025 0.031 0.031 0.040 0.047 0.056 0.062 0.078 0.094 0.109 0.125
Max. 0.146 0.168 0.192 0.220 0.231 0.271 0.311 0.351 0.464 0.556 0.651 0.740 0.834
Min. 0.135 0.156 0.181 0.207 0.218 0.259 0.297 0.336 0.448 0.540 0.635 0.723 0.815
Min. 0.035 0.040 0.047 0.047 0.062 0.078 0.093 0.109 0.125 0.156 0.171
Min. 0.020 0.025 0.031 0.031 0.034 0.031 0.047 0.062 0.062 0.078 0.093
Max. 0.156 0.178 0.208 0.220 0.261 0.319 0.373 0.429 0.496 0.618 0.711
Min. 0.145 0.166 0.195 0.207 0.248 0.305 0.359 0.414 0.480 0.602 0.695
Indentation optional
Pan Head Type AB Tapping Screw
Fillister Head Type BF Tapping Screw
Hex Head [Note 11)3 Type B Tapping Screw
Hex Washer Head Type BT Tapping Screw
Representative Examples of Helical Spring Lock Washer Sems
THREAD DIAMETER-PITCH COMBINATIONS Pan Head Screw Filister Head Screw Hex Head Screw [Noted)] Hex Washer Head Screw Washer Washer Washer Washer Section Section Section Section Washer Washer Washer Washer Washer Thick- Outsd ie ie Thick- Outsd ie Inside Thick- Outsd Thick- Outside i meter Width ness Da i meter i meter Width ness Da i meter Width ness Da Da i meter Width ness Da Max. Min. Min. Min. Max. Min. Min. Min. Max. Min. Min. Min. Max. Min. Min. Min. Max. Min. 0.101 0.096 0.047 0.031 0.201 0.190 0.035 0.020 0.179 0.166 0.040 0.025 0.187 0.176 0.047 0.031 0.201 0.190 0.112 0.107 0.050 0.034 0.218 0.207 0.035 0.020 0.190 0.177 0.047 0.031 0.214 0.201 0.050 0.034 0.218 0.207 0.121 0.116 0.062 0.034 0.253 0.240 0.047 0.031 0.223 0.210 0.047 0.031 0.223 0.210 0.062 0.034 0.253 0.240 0.135 0.130 0.062 0.034 0.267 0.254 0.047 0.031 0.237 0.224 0.047 0.031 0.237 0.224 0.062 0.034 0.267 0.254 0.144 0.138 0.078 0.031 0.308 0.294 0.047 0.031 0.246 0.232 0.055 0.040 0.262 0.248 0.078 0.031 0.308 0.294 0.162 0.156 0.081 0.056 0.332 0.318 0.055 0.040 0.280 0.266 0.062 0.047 0.294 0.280 0.081 0.056 0.332 0.318 0.188 0.181 0.081 0.056 0.358 0.343 0.062 0.047 0.320 0.305 0.070 0.056 0.336 0.321 0.081 0.056 0.358 0.343 0.217 0.209 0.120 0.062 0.465 0.449 0.077 0.063 0.379 0.363 0.109 0.062 0.443 0.427 0.120 0.062 0.465 0.449 0.278 0.270 0.125 0.078 0.536 0.520 0.109 0.062 0.504 0.488 0.125 0.078 0.536 0.520 0.125 0.078 0.536 0.520 0.338 0.330 0.141 0.094 0.628 0.612 0.125 0.062 0.596 0.580 0.141 0.094 0.628 0.612 0.141 0.094 0.628 0.612 0,156 0.109 0.716 0.700 0.397 0.388 0.171 0.125 0.812 0.793 0.460 0.451
Nomn i al Szi e [Note (2}] or Basci Screw Da i meter 4 0.1120 5 0.1250 6 .1380 7 0 0.1510 8 0.1640 10 0.1900 12 0.2160 0.2500 6V4 0.3125 3Z16 Z8 0.3750 .4375 Vi6 0 0.5000 V2 GENERAL NOTES: (a) For additional requirements, refer to Secto i ns 2 and 3. (b} Dm i enso i ns of helical spring lock washers applicable to "not recommended for new design" status round and truss head screw sems and Type A tapping screw sems are documented for reference purposes in Appendxi B. NOTES: {1} The regular trimmed or upset hex head screws shall apply for the washers shown. Where upset large hex head screws in szi es No, 4, 5, 8, 12, and 1/4 in. are specified by the purchaser, the washers shown for the corresponding size hex washer head screw shall apply. Refer to appropriate tables for hex head tapping screws in ASME B18.6.4. (2) Where specifying nominal szi e in decimals, zeros precedn i g the decm i al and in the fourth pa l ce shall be omited. Reprinted from ASME B18.13a-1998, by permission of the American Society of Mechanical Engineers. All rights reserved. Copyright © 2005 by The McGraw-Hill Companies
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S
E
M
S t a n d a r d
T a b l e s
(continued)
Colar on countersunk washers optional
Oval Head Type B Tappn i g Screw
Pan Head Type AB Hex Head [Note (IHHex Washer Head Type Hex Cap Screw Tappn i g Screw Type D Tappn i g Screw T Tappn i g Screw Representative Exampe l s of External Tooth Lock Washer Sems
Co py rig hte dM ate ria l
Flat Head Machn ie Screw
indentation optional
Nomn i al Szi e [Note (2)] or Basci Screw Da i meter 2 0.0860 3 0.0990 4 0.1120 5 0.1250 6 0.1380 7 0.1510 8 0.1640 10 0.1900 12 0.2160 V4 0.2500 0.3125 % 0.3750
DIMENSIONS OF EXTERNAL TOOTH LOCK WASHERS FOR SEMS Pan Head Screw Hex Head and Hex Cap Screws [Note (D] Flat and Oval Head Screws Hex Washer Head Screw Washer Washer Washer V Washer Washer Outsd ie Washer Washer Outsd ie Outside F u l s h to Thci kness Thci kness Da i meter Thci kness Da i meter Thci kness Da i meter Mn i us l rance of Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Toe 0.016 0.010 0.180 0.170 0.016 0.010 0.180 0.170 0.016 0.010 0.180 0.170 0.014 0.009 0.016 0.010 0.205 0.195 0.016 0.010 0.205 0.195 0.016 0.010 0.205 0.195 0.019 0.014 0.009 0.018 0.012 0.230 0.220 0.018 0.012 0.230 0.220 0.018 0.012 0.230 0.220 0.022 0.019 0.015 0.020 0.014 0.255 0.245 0.020 0.014 0.255 0.245 0.020 0.014 0.255 0.245 0.024 0.020 0.016 0.022 0.016 0.285 0.270 0.022 0.016 0.285 0.270 0.022 0.016 0.317 0.306 0.026 0.020 0.016 0.047 0.022 0.016 0.285 0.270 0.022 0.016 0.285 0.270 0.022 0.016 0.317 0.306 0.030 0.020 0.016 0.023 0.018 0.320 0.305 0.023 0.018 0.320 0.305 0.023 0.018 0.317 0.306 0.036 0.025 0.019 0.024 0.018 0,381 0.365 0.024 0.018 0.381 0.365 0.024 0.018 0.406 0.395 0.041 0.025 0.019 0.027 0.020 0.410 0.395 0.027 0.020 0.410 0.395 0.027 0.020 0.406 0.395 0.025 0.019 0.047 0.028 0.023 0.510 0.494 0.028 0.023 0.475 0.460 0.028 0.023 0.580 0.567 0.028 0.023 0.060 0.034 0.028 0.610 0.588 0.034 0.028 0.580 0.567 0.034 0.028 0.654 0.640 0.034 0.028 0.072 0.040 0.032 0.760 0.740 0.040 0.032 0.660 0.640 0.040 0.032 0.760 0.740 Indentation optional'
Pan Head Machine Screw
Fillister Head Type B Tapping Screw
Hex Head [Noted}] Hex Washer Head Type AB Tapping Type T Tapping Screw Screw Representative Examples of internal Tooth Lock Washer Sems
Hex Cap Screw
DIMENSIONS OF INTERNAL TOOTH LOCK WASHERS FOR SEMS Pan, Filister, Hex [Note (1)1. and Hex Washer [Note (2)] Head Screws Nominal Washer Size [Note (3)] Outside Diameter Washer Thickness or Basci Screw Diameter Max. Min. Max. Mm. 0.175 2 [Note (2)] 0.0860 0.010 0.185 0.016 0.215 3 [Note (2)] 0.0990 0.016 0.010 0.225 4 [Note (2)1 0.1120 0.258 0.018 0.012 0,268 0.258 5 [Note (2)] 0.1250 0.018 0.012 0.268 6 0.278 0.1380 0.016 0.288 0.022 7 0.278 0.1510 0.022 0.016 0.288 8 0.327 0.1640 0.023 0.018 0.338 0.372 10 0.1900 0.018 0.383 0.024 0.396 12 0.2160 0.027 0.020 0.408 V4 0.478 0.466 0.2500 0.028 0.023 5 0.610 0.597 0.3125 0.034 0.028 Z16 0.692 0.678 0.3750 0.032 0.040 % GENER AL NOTES: (a) For additional requirements, refer to Sections 2 and 4. (b) Dimensions of internal tooth lock washers applicable to "not recommended for new design" status round and truss head screw sems and Types A and C tapping screw sems are documented for reference purposes in Appendix C. NOTES: O) The regular trimmed or upset hex head screws shall apply except for sizes No. 4, 5, 8, 12, and 1/4 in., which shall have upset large hex head screws. Refer to appropriate tables for hex head machn i e and tapping screws in ASME B18.6.3 and ASME B18.6.4, respectively. Refer to appropriate tables for hex cap screws in ASME B18.2.1. (2) Hex washer head sems are not available in sizes smaller than No. 6. (3) Where specifying nominal size in decimals, zeros preceding the decimal and in the fourth place shali be omitted.
Reprinted from ASME B18.13a-1998, by permission of the American Society of Mechanical Engineers. All rights reserved. Copyright © 2005 by The McGraw-Hill Companies
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S t a n d a r d
T a b l e s
Crown height
Pan Head Type AB Tappn i g Screw and Type L Regua l r Washer
(continued) Indentation optional
Filister Head Type B Tappn i g Screw and Type L Narow Washer
Hex Head !Note <1}j Hex Washer Head Type T Tappn i g Screw and Machn i e Screw 3nd i e Washer Type H Regua l r Washer Type H Wd
Hex Cap Screw
Co py rig hte dM ate ria l
S E M
Representative Exampe l s of Conical Spring Washer Sems
Nominal Size [Note (2)] or Basci Screw Diameter
6
0.1380
8
0.1640
10
0.1900
12
0.2160
V4 0.2500
5
Z16 0.3125
3
Z8 0.3750
7
Z16 0.4375
V2 0.5000
Washer Series Narrow Regular Wd ie Narrow Regular Wd ie Narrow Regular Wd ie Narrow Regular Wd ie Narrow Regular Wd ie Narrow Regular Wd ie Narrow Regular Wd ie Narrow Regular Wd ie Narrow Regua lr Wd ie
DIMENSIONS OF CONICAL SPRING WASHERS FOR SEMS Pan, Filister, Hex [Note {1}], Hex Washer Head, and Hex Cap Screws Washer Outside Type H Washer Type L Washer Crown Crown Height Height Thickness Thickness Max. Min. Basci Max. Min. Max. Min. Basci Max. Min. Max. Min. 0.320 0.307 0.025 0.029 0.023 0.025 0.015 0.035 0.040 0.033 0.025 0.015 0.446 0.433 0.030 0.034 0.028 0.025 0.015 0.040 0.046 0.037 0.025 0.015 0.570 0.557 0.030 0.034 0.028 0.031 0.021 0.040 0.046 0.037 0.029 0.019 0.383 0.370 0.035 0.040 0.033 0.025 0.015 0.040 0.046 0.037 0.025 0.015 0.508 0.495 0.035 0.040 0.033 0.030 0.020 0.045 0.050 0.042 0.026 0.016 0.640 0.620 0.035 0.040 0.033 0.037 0.027 0.045 0.050 0.042 0.040 0.030 0.446 0.433 0.035 0.040 0.033 0.025 0.015 0.050 0.056 0.047 0.025 0.015 0.570 0.557 0.040 0.046 0.037 0.027 0.017 0.055 0.060 0.052 0.026 0.016 0.765 0.743 0.040 0.046 0.037 0.036 0.026 0.055 0.060 0.052 0.034 0.024 0.446 0.433 0.040 0.046 0.037 0.025 0.015 0.055 0.060 0.052 0.025 0.015 0.640 0.620 0.040 0.046 0.037 0.033 0.023 0.055 0.060 0.052 0.026 0.016 0.890 0.868 0.045 0.050 0.042 0.044 0.034 0.064 0.071 0.059 0.033 0.023 0.515 0.495 0.045 0.050 0.042 0.025 0.015 0.064 0.071 0.059 0.025 0.015 0.765 0.743 0.050 0.056 0.047 0.033 0.023 0.079 0.087 0.074 0.032 0.022 1.015 0.993 0.055 0.080 0.052 0.040 0.030 0.079 0.087 0.074 0.039 0.029 0.640 0.620 0.055 0.060 0.052 0.026 0.016 0.079 0.087 0.074 0.026 0.016 0.890 0.868 0.064 0.071 0.059 0.041 0.031 0.095 0.103 0.090 0.029 0.019 1.140 1.118 0.064 0.071 0.059 0.044 0.034 0.095 0.103 0.090 0.040 0.030 0.765 0.743 0.071 0.079 0.066 0.025 0.015 0.095 0.103 0.090 0.025 0.015 1.015 0.993 0.071 0.079 0.066 0.043 0.033 0.118 0.126 0.112 0.033 0.023 1.265 1.243 0.079 0.087 0.074 0.047 0.037 0.118 0.126 0.112 0.045 0.035 0.890 0.868 0.079 0.087 0.074 0.028 0.018 0.128 0.136 0.122 0.026 0.016 .095 0.103 0.090 0.041 0.031 0.128 0.136 0.122 0.038 0.028 1.140 1.118 0 1.530 1.493 0.095 0.103 0.090 0.059 0.049 0.132 0.140 0.126 0.049 0.039 1.015 0.993 0.100 0.108 0.094 0.031 0.021 0.142 0.150 0.136 0.030 0.020 1.265 1.243 0.111 0.120 0.106 0.043 0.033 0.142 0.150 0.136 0.037 0.027 1.780 1.743 0.111 0.120 0.106 0.062 0.052 0.152 0.160 0.146 0.052 0.042
Copyright © 2005 by The McGraw-Hill Companies
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MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
17
Co py rig hte dM ate ria l
O-RINGS
8 Unusual Appc ilato ins for OR -n igs 16 Unusual Appc ilato ins for the OR -n ig Look at OR -n igs Diferently OR -n igs Sov le Desg in Probelms I OR -n igs Sov le Desg in Probelms M 7 More Appc ilato ins for OR -n igs Desg in Recommendao itns for OR -n ig Seas l OR -n ig Seas l for Pump Vav les
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17-2 17-4 17-6 17-8
17-10 17-12 17-14 17-16
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8
U n u s u a l
A p p l i c a t i o n s
f o r
O - R i n g s
Playing many different roles, O-rings can perform as protective devices, hole liners, float stops, and other key design-components. Robert O. Parmley
Co py rig hte dM ate ria l
frpmfr
Shockle
Shackle irons
Rope
O-Tt'ng$
0-ring-
leaf springs,
: Q-ring
Bushing
leaf spring
V pulley-
Compression area
CUSHION RGjPE IN V-SECtlON PULLEY
PROTECT METAL SURFACES DURING SMALL RELATIVE MOVEMENTS
Oaring.
0~ring
Alternative positions
float action
Adhesive bond
Q-ring
Q-ring
Position post FIoaf
Q-ring
OUICKLY ADJUST FLOAT STOP
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0 RINGS CONFORM TO [RREGULAR CONTOURS
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Co py rig hte dM ate ria l
Swing shaft is - !• centered by Q-ring
Lever
O-ring^
Stem
Rods
Oaring makes strong aligning band \ A
Adhesive, bond i
\Hbifsihg
Large \ clearance Orring
Oaring
A
Cmtig
Eiectricoi wires Bi
B LINE HPLES TO CUSHION LEVERS (A) AND STABiLlZ^ SHAFTS !NiLARGE HOLES (B)
REtAfN PARTS (A) OR WIRES (B)
'Push
Funnel
Push • Button,
O-ring
Q-ring
Post
'Contact point
Q-ring'T
B
A
CUSHION PRESSURE BUTTQNS
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SEAL AND"CUSH(ON FUNHEL
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1 6
U n u s u a l
A p p l i c a t i o n s
f o r
t h e
O - R i n g
This handy little component finds a place in pumps, drives, glands, shock-mounts, pivots, knobs, valves and seals.
Co py rig hte dM ate ria l
James F. Machen
Toper up to lj-°
Tapered bore . in diecasting, plus low-cost pump for Example: carburetor
. . loose-fitting O-ring, gives low-pressure applications. accelerator-pump.
JQ in.
to JQ in. dio.
Sealed pivot . . . allows transmittal of multidirectional/ mechanical movement to hydraulically or pneumatically isolated system. For high-temperature seals, silicone rubber can often solve the problem—but always guard against excessive "set/
Beit drive
Friction drive
Simple drives . . . utilize not only O-ring but its physical properties also—high friction and elasticity.
Rollover-
Single-ring gland . . . is ideal for low pressures and highviscosity fluids. If necessary, another ring may be installed.
Shaft seal . . . may be held by rolling the thin body-wall over the O-ring. Bolt seal (8) is squeezed into countersink when bolt is tightened. Cross-sectional area of countersink must not be less than that of O-ring since molded rubber is practically incompressible when confined.
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Plunger Pressure side
Pin
Pressure side
Co py rig hte dM ate ria l
Plug
One-way pressure . . . applications require O-ring seals to be supported on pressure side only. Seal may be movable (9) as in grease gun, or static (10) as in pipe plug. Anchor ring to plunger and plug for greater convenience and reliability.
A
Friction grip . . . on knob not only allows better grip but insulates fingers from heat or electricity. It al:o improves appearance on both mockups and working models.
B
Miniature shock-mount . . . will isolate equipment from vibrations in accordance with behavior of visco-elastic materials
Checkvalves . . . may have ball free (A); or springloaded (B). Back pressure will always force ball onto seat provided that gravity first helps locate ball on seat. Heavier-duty checkvalve (14) can be opened to allow back pressure to escape if necessary for shutdown etc.
High-pressure checkvalve . . . shown here cannot allow release of backpressure but could be easily modified to do this by letting valve stem protrude.
Butterfly valve . . . can become a checkvalve if it is unbalanced; otherwise, it will act as normal two-way valve.
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L o o k
a t
O - R i n g s
D i f f e r e n t l y
Sure they're seals, but they can also do a variety of other jobs as well as more sophisticated pieces of hardware
Co py rig hte dM ate ria l
Robert O. Parmley
{'Connectionflange) Pipe or heavv wall tube
Pressed wood
-pefa/Y waiher
Ch-fincf
Q-ririg
A
Typ.
K
A
TQ align Q-ring, use smaifer fD and insert pipe sieeve into connection flanges
C
№
Sealing gasket
Plastic reservoir
T
Marring protection
Liquid fill entry
O-rlna
Work piece component
Moaniposf
Orringy
Pressure
Typical openings
Metal strainer cup
Boil {rollers Cup rest and strainer seal
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Aligning bumper
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Bed-
Co py rig hte dM ate ria l Pressure
0- ring
Mounting block
O-ring
Plastic bolt
$dh6siv$ Posf
pin \ :
masfieri
Compression Ml\sedt bowl hole face bnfo block surface r ;
Gifts$ sphere
Bowl sealing
Housing:
p-ring
Shock absorption
Housing fwif
Confgcf point
Oaring
Work pressure
Air vent
Wire
Release Q~ring
Lever handle Cam lock, lever
Lever stop
Chamber seal
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O - R i n g s
S o l v e
D e s i g n
P r o b l e m s
I
Rubber rings provide for thermal expansion, protect surfaces, seal pipe ends and connections, and prevent slipping.
Co py rig hte dM ate ria l
Robert O. Parmley
Expansion and 0-ring \ provide? . for expansion. on.(t\ comfaction, area.'... con traction, of a '• stem,, shaft,7of past \
ABSORBS EXPANS(OfI
CuM ]• grooves'"
Pressure
: r&ciprocafe$
[
\Sfem
Support biock 'Q^rlng
Pfasiic
Pipe c^
Water or Me am pipe
PROtECTSiPLASTiC
SEALS PIPE E^D
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Weta/
wm :
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Vcring\
Co py rig hte dM ate ria l Liquid flow
SEALS IN VAPQR nURlNGFaLIHal
Hose-
O-ring
Chamber
inserf tube-
Seal seaf'
Adhesive 'bond-
Oaring
tank
Elow
Volatile liquid
Imerf inxf/lk Me. for manuof use
Sealing seaf
SEALS SEPARABLE FLOWLINE I
Typical ink boffie
Adhesive bond
O-ring
Siapesurifope'
PREVENTS SLIP
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O - R i n g s
S o l v e
D e s i g n
P r o b l e m s
Il
More examples of how rubber rings provide seals for shafts, lids, nozzles, and elbows, and also protect corners, cushion metal surfaces.
Co py rig hte dM ate ria l
Robert O. Parmley
0-ring-
SlOW rotation
Clearance
Bearing
Support post
Shaft-
Plastic housing
SEAL FOR SLOWLY ROTATING SHAFT
Suction tube
O-ring
Tubes
0'rings
Thin receiver bog
Thin rubber or plastic tube
RETAINER FOR TUBE-TO-TUBE CONNECTIONS
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CUMP-BAMO FOR SIMPLE BAG ATTACHMENT
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Co py rig hte dM ate ria l
WoIi
Nozzle
O-ring
Clearance
Thumb screwLidTan/f.
Swivel
O-ring compresses when screw is iightened
LIQUID- OR AIR-NOZZLE SEAL
Expander disk
LOCKtNG-SEAl FOR LID ASSEMBLY
Component-
A Fillet curve
Component
Quartered^ Q-rings
Turn handle (tighten for iocH position, thus compressing O-ring)
B Exterior curve
-Adhesive bond
O-ring
Swing area
Component piece
Typicof section
Top rotator
O-rings-use amount needed for proper cushioning (no metai wear)
Bottom rotator
PROTECTIVE MOLDING MADE FROM ORING SEGMENTS
CUSHION-RING FOR SWIVEL OR LIGHTWEIGHT ROTATING COMPONENTS
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7
M o r e
A p p l i c a t i o n s
f o r
O - R i n g s
For an encore to the roundup in the previous issue, O-rings are shown here performing in valves, on guide wheels, and as cushioning, etc. Robert O. Parmley
Chamber won
Co py rig hte dM ate ria l
Chamber Pin-seat with caulking
Flow grooves
Flow
Shut
Open
Pin
V- ring
Flow grooves
Siot
O-ring groove
B
Mount piofe
Slot
A
LOW-COST VALVE has easily changed O-ring, plus flutes for liquid flow, and caulked pin (A). Simpler valve (B) is adequate at less cost.
O-ring
Add or subject O-rings for desired height
CUSHION-RINGS for vibration isolation or adjustment are quickly adjustable by merely adding or removing O-rings from the stack.
Bearing
Shaft-
Surface
Work piece-
Base
Horizontal -application
PROTECTED GUIDE WHEELS are often needed to guide, move, or align work. An O-ring here provides both friction and protection.
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Co py rig hte dM ate ria l
Blade
0 -ring-
ffow
Adhesive bond
Glass funnel
Contact surface
Sec. A-A
PROTECTION RINGS for push-pull or press action insulate against electrical shock/ protectfingersagainst metal edges.
Seam,
Or ring.
REPLACEABLE SEALS protect against spilled T acids While cushioning funnels and similar glass apparatus against breakage*
Q-ring
Sp/if holding stem-
SPLIT STEMS can be held firmly with a suitable size O-ring, One or more can be placed at varying positions on the steim
Glass sheet
Chamber WQ)7
Glass pane
AdheMm bond:
V-rings
WORKING-TABLE FOR GLASS or other delicate materials has O-ring resting pads set into surface at over-all or grouped locations.
Copyright © 2005 by The McGraw-Hill Companies
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Rest pad
D e s i g n f o r
R e c o m m e n d a t i o n s
O - R i n g
S e a l s
J. H. Swartz
Rectangulor
Vee
Clearance E
Approx. Q4d
Co py rig hte dM ate ria l
Dovetail 0.86dmax.
Section diameter
grooves are recommended for most applica1 Rectangular tions, whether static or dynamic. Slightly sloping sides
(up to 5 deg) facilitate machining with form tools. Where practical, all groove surfaces should have the same degree of finish as the rod or cylinder against which the O-ring operates. The Vee type groove is used for static seals and is especially effective against low pressures. The dovetail groove reduces operating friction and minimizes starting friction. The effectiveness of the seal with this groove is critical depending upon: pressure, ring squeeze and angle of undercut. In general, the groove volume should exceed the maximum ring volume by at least 15 percent.
Groove length D
Groove Initial width squeeze C
To insure a positive seal, a definite initial squeeze or inter2is approximately ference of the ring is required. As a rule, this squeeze 10 percent of the O-ring cross sectional diameter d. This results in a ring contact distance of approximately 40 percent under zero pressure and can increase as much as 80 percent of the cross section diameter depending on pressure and composition of the ring. Starting friction can be reduced somewhat by decreasing the amount of squeeze but such a seal would be only moderately effective at pressures above 500 psi. Table I lists the recommended dimensions and tolerances for O-ring grooves for both static and dynamic applications.
EXTERNAL GROOVES
INTERNAL GROOVES
Less than 30°
less than 30°
On small diameters, to facilitate machining, O-ring 3 grooves should be located on the ram or rod rather than
on an inside surface. For larger diameters, grooves can be machined either way. One important factor is that the rubbing surfaces must be extremely smooth. The recom-
mended dimensional data in Table I and listed under dynamic seals should be used for these applications. All cylinders and rods should have a gradual taper to prevent damage to the O-ring during assembly. Equations are listed for calculating limiting dimensions for both external and internal grooves.
Sharp comer
PISTONS
Good
Poor
0.060" min. radius
RODS Sharp corner Poor
Good
To facilitate assembly, all members which slide over O-rings 6alternative should be chamfered or tapered at an angle less than 30 degrees. An method is to use a generous radius. Such details prevent any possibility of pinching or cutting the O-ring during assembly.
Copyright © 2005 by The McGraw-Hill Companies
Undercut all sharp edges, or cross7 drilled ports over which O-rings
must pass. While under pressure, rings should not pass over ports or grooves.
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Table I—Dimensional Data for Standard AN or JJ.C. O-Rings and Gaskets For Static Seals d Actual Section Diameter
For Dynamic Seals
R IE D C C Diametral Groove Diametral Groove Groove Minimum Diametral Eccentricity Squeeze* Width Squeeze* Width Clearance (maximum) (minimum) +0.000 (minimum) +0.000 Length** Radius (maximum) -0.005 -0.001
Co py rig hte dM ate ria l
Specification AN 6227 or Nominal Ring T. I. C. Section O-Ring Dash Number Diameter 1 to 7 8 to 14 15 to 27 28 to 52 53 to 88
1/16 3/32 1/3 3/16 1/4
O.O7O±O.OO3 0.1O3dbO.O03 0.139±0.004 O.21O±O.OO5 O.275±0.006
0.015 0.017 0.022 0.032 0.049
0.052 0.083 0.113 0.173 0.220
AN 6230 or J. I. C. gaskets l t o 52
1/8
0.139=fc0.004
0.022
0.113
0.057 0.090 0.123 0.188 0.240
0.010 0.010 0.012 0.017 0.029
3/32 9/64 3/16 9/32 3/8
1/64 1/64 1/32 3/64 1/16
0.005 0.005 0.006 0.007 0.008
0.002 0.002 0.003 0.004 0.005
3/16
1/32
0006
0.003
Note: All dimensions are in inches. * Diametral squeeze is the minimum interference between 0-Ring cross section diameter d and gland widtli C. ** H space is limited, the groove length D caa be reduced to a distance equal to the maximum O-Ring diameter d plus the static seal squeeze.
FACE SEAL GROOVES
9ing I.D.
•Ring OJ).
Under, cut
Under cut
For internal pressure only (A)
Clearance /ess than squeeze
For pressure or vacuum
Excessive clearance
(B)
(A)
(B))
For static face seals, two types of grooves are shown. 4chining. Type (A) is more commonly used because of simpler maGroove depths listed in Table I under static seals
clearances should never exceed one-half of the 5doesRadial recommended O-ring squeeze even where the pressure not require the use of a close fit between sliding parts.
apply to this application. In high pressure applications where steel flanges are used, slight undercutting of one face (not exceeding 0.010 in.) minimizes possible O-ring extrusion.
Under these conditions, if the shaft is eccentric (A), the ring will still maintain its sealing contact. (B) Excessive clearance results in the loss of sealing contact of the O-ring. CHECK VALVES
Clearance
Ring extrusion
(A)
(A)
CA)
For rotating shafts
Poor
Pressure will bypass seal
Stomping (B)
Metal contact
Poor
Good
POPPET VALVES R~min.O-ring cross section radius
(B) Good (8) Clearance
PLUG SEAL
Metal-to-metal contact of the inner 8avoided. mating surfaces (A) should be Clearances should be per-
stamping (A) pressed in 9sures.Simple housing is for low speeds and pres(B) Chamfered corners of plug
mitted only on inner surfaces (B).
makes a recess for an O-ring.
Copyright © 2005 by The McGraw-Hill Companies
\A R e c t a n S u l a r grooves (A) should I " be normal to the sealing surface. Special grooves (B) avoid the washout of O-rings during pressure surges.
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O - R i n g
S e a l s
f o r
P u m p
V a l v e s
Robert O. Parmley
PIPE
Co py rig hte dM ate ria l
O-RING
UNION
A - G o m b i n a t i o n P u m p V a l v e The C P V O-ring seal fitting (a Navy standard) uses an O-ring which is inserted in the packing-gland recess on the face or the union which has been silver-brazed to the end of a pipe. The union and pipe are sometimes called a "tailpiece."
HANDLE
O-RING
N O Z Z L E HEAD
H O S E BIB
HOSE
B - H a n d - A d j u s t e d P u m p N o z z l e The discharge end (nozzle head) of this portable pump unit has the spray adjusted by manually turning the nozzle head. The O-ring maintains a positive, water-tight seal for any adjusted position.
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l ACTION -
HANDLE
RETAINER
H O S E BIB
O-RING
PISTON ROD
C-Manual P u m p Seal The O-ring, which is seated by the threaded retainer, provides a water-tight seal for the up & down action of the piston rod.
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
18
Co py rig hte dM ate ria l
RETAINING RINGS Compas rions of Retan in ig Rn igs Versus Typc ial Fasteners Retan in ig Rn igs Ad i Assembyl, I Retan in ig Rn igs Ad i Assembyl, Il Coupn ilg Shafts wtih Retan in ig Rn igs The Versate li Retan in ig Rn ig The Mup tile l-Purpose Retan in ig Rn ig More Work for Round Retan in ig Rn igs Defe lcto ins of Perpendc iua lry l Loaded Split Cricua lr Rn igs m I prove Desg in wtih Retan in ig Rn igs
Copyright © 2005 by The McGraw-Hill Companies
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18-2 18-4 18-6 18-8 18-12 18-16 18-18 18-20 18-22
C o m p a r i s o n s V e r s u s
o f
T y p i c a l
R e t a i n i n g
R i n g s
F a s t e n e r s
A variety of basic applications show how these rings simplify design and cut costs.
Co py rig hte dM ate ria l
Howard Roberts
Collar- width of material saved
Broken lines here and on other dm wings show how much metal is scrapped by machining, or saved by using spring ring. .
MACHINED SHOULDERS are replaced with savings in material, tools and time. Grooving for ring can be done during a cut-off, or other machining operation.
RINGS THAT CAN REPLACE cotter pin and washer are economical since only one part is required and pin-spreading operation is not needed thus cutting time and costs^
Copyright © 2005 by The McGraw-Hill Companies
WHEN COLLAR AND SETSCREW are substituted by ring, risk of screw vibrating loose is avoided. Also, no damage to shaft by screw point occurs —a frequent cause of trouble.
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Co py rig hte dM ate ria l RETAIN COMPONENTS on diecastings with a simple-to-use grip ring. Slipped over the end of the shaft, the ring exerts a frictional hold against axial displacement of the shaft.
SHOULDER AND NUT are replaced by two retaining rings. A flat ring replaces the shoulder, while a bowed ring holds the component on shaft for resilient end-play take-up.
COVER-PLATE ASSEMBLY has been redesigned (lower drawing) to avoid use of screws and machined cover-plate. Much thinner wall can be used—no drilling or tapping.
THREADED INTERNAL FASTENERS are costly because of expensive internal threading operation. Simplify by substituting a selflocking retaining ring—see lower drawing.
HEAT-FORMED STUD provides a shoulder against retained parts but must be scrapped if the parts must be disassembled for service. Self-locking ring can be easily removed.
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
R
e
t
a
i
n
i
n
g
R
i
n
g
s
A
i
d
A
s
s
e
m
b
l
y
,
I
By functioning as both a shoulder and as a locking device, these versatile fasteners reduce machining and the number and complexity of parts in an assembly.
Co py rig hte dM ate ria l
Robert O. Parmley
WorkN
Adjustment^ direction
Locator pin
Jig frame
Internal selflocking ring
Internal self-locking ring supports a locator. Elevation of the pin may be altered in the entry direction only; the pin won't push down into the frame
Connecting rod retainer
Retaining ring
Two part ring 2-pchousing
Slow-moving piston of hydraulic motor is assembled to the crank throw by two retainers. These are held in place by two retaining rings that fit into grooves in the crankthrow
Bearing Two-piece interlocking retaining ring serves to hold a two-piece assembly on a rotating shaft, and is more simple than a threaded cap, a couple of capscrews or other means of assembly
Courtesy: American Machinist: Published by Penton Media, Inc. Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Co py rig hte dM ate ria l
Free ring
Groove detail
Roller
Roller axle
Bowed lockingprong ring
Heavy-duty Two types of rings may be used on one assembly. Here permanent-shoulder rings provide a uniform axle step for each roller, without spotwelding or the like. Heavy-duty rings keep the rollers in place
Reinforced circular self-locking
Tapered -section self-locking
Triangular self-locking
Reinforced E- ring Snug assembly of side members to a casting with cored hole is secured with two rings: 1—spring-like ring has high thrust capacity, eliminates springs, bow washers, etc; 2—reinforced E-ring acts as a retaining shoulder or head. Each ring can be dismantled with a screwdriver
Triangular nut Triangular retaining nut eliminates the need for tapping mounting holes and using a large nut and washer. Secure mounting of small motors and devices can be obtained in this manner
These three examples show seJf-locking retaining rings used as adjustable stops on support members (pins made to commercial tolerances): A—external ring provides positive grip, and arched rim adds strength; B—ring is adjustable in both directions, but frictional resistance is considerable, and C—triangular ring with dished body and three prongs will resist extreme thrust. Both A and C have one-direction adjustment only
Copyright © 2005 by The McGraw-Hill Companies
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R e t a i n i n g
R
i
n
g
s
A
i
d
A
s
s
e
m
b
l
y
,
I l
Here are eight thought-provoking uses for retaining rings.
Co py rig hte dM ate ria l
Robert O. Parmley
Heavy duty ring
Adjustment: up only
Retaining ring
Support rod
Retaining ring-
Hanger
Lever
Axial pin for lever is secured with a heavyduty ring, making a neat, strong assembly
Hook
Ring offer assembly
Free ring
Pin
Detail of groove
Hanger hook is held a t desired height by a self-locking external ring. A multitude of adjustments can be made without trouble
Retaining ring-
Belt
Ring
Bail
Housing
Sleeve or valve ball seat
Retaining ring Shaft Belt alignment is assured by using permanent shoulder retaining rings. The rings are crimped into the shaft grooves for a permanent, clean, and inexpensive flange. A retainer ring of this type has a high capacity for thrust loads
Coil spring
A sleeve or ball seat valve is safely retained by a ring that acts like a wedge in the outer groove. Rigid end-play take-up is provided
Courtesy: American Machinist: Published by Penton Media, Inc. Copyright © 2005 by The McGraw-Hill Companies
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Plastic tubing
HousingVacuum on
Housing illustrated transparent to reveal internal design Retaining ring
Retaining ring
Key.
Co py rig hte dM ate ria l
Plastic ball
Ring,
Housing
Shaft
Tamper-proof lock for a shaft in a housing provides location of the shaft and at the same time retains the key. Heavy axial loading and permanent retention of the key are double values in this application
Vacuum released Internal self-locking ring supports the plastic ball valve when the vacuum is released, thus providing a support during the "off" cycle. Air or liquid is released when ball is at rest and exits through the areas between the grip points of the ring, which is adjustable at entry position
Ring half
Observation lid
Stem Weight disc
Ring
Ring groove
Rubber stopper with internal threaded sleeve
Drain hole
Triangular retainer nut positions and unifies components of the tank drain assembly. The triangular nut eliminates the need for a large standard nut and lockwasher or springtype component and simplifies the design
Copyright © 2005 by The McGraw-Hill Companies
Ring half
Observation lid on tubing makes it possible to inspect wiring at will. The two-part balanced retainer ring has identical semicircular halves, which are held together by the interlocking prongs at the free ends
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Tube
C o u p l i n g
S h a f t s
w i t h
R e t a i n i n g
R i n g s
These simple fasteners can provide an original way around certain design snags. For example, here are eight ways they're used to solve shaft-coupling problems. Robert O. Parmley
Co py rig hte dM ate ria l
Sleeve
Pin, Sleeve, and Ring
Pre-assembly position
Ring groove
Press fit pin
This inexpensive connection is for light torques and moderate loads where accurate positioning is not required. A heavy-duty ring is used to resist high-impact and thrust loads.
SSeeve, Key, and Ring Key
Shaft
Retaining ring
Sleeve
Ring groove
Retaining ring
Crimped afier assembly
Crimping the retaining ring into the groove produces a permanent, simple, and clean connection. This method is used to avoid machining shoulders in expensive materials, and to permit use of smaller-diameter shafts. When the ring is compressed into a V-shaped groove on the shaft, the notches permanently deform into small triangles, causing a reduction of the inner and outer diameters of the ring. Thus, the fastener tightly grips the groove, and provides a 360-deg shoulder around the shaft. Good torsional strength and high thrustload capacity is provided by this connection.
Courtesy: Machine Design: Published by Penton Media, Inc. Copyright © 2005 by The McGraw-Hill Companies
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Two-Shaft
Splice
a
Retaining ring
Co py rig hte dM ate ria l
Shaft half
Blade half
Retaining ring
b
A balanced two-part ring provides an attractive appearance in addition to withstanding high rotational speeds and heavy thrust loads, a. The one-piece ring, b, secures the shafts in a high-torque capacity design.
End-Range
Connection
Heavy-duty retaining ring
Connection pin
Shaft
Set screw
Flange
This assembly for heavy-duty service requires minimum machining. Ring thickness should be substantial, and extra ring-section height is desirable,
Copyright © 2005 by The McGraw-Hill Companies
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C o l l a r , Rings, a n d T h r e a d e d S h a f t Shaft
Collar
Co py rig hte dM ate ria l
a
Adjustment
Tapered-section, self-locking ring
b
Shaft
Ring-groove clearance
Equals ring-groove clearance for assembly
For a connection that requires axial shaft adjustment, the self-locking ring requires no groove, a. An alternate solution, b, uses an inverted-lug ring seated in an internal groove. Extra ring-section height provides a good shoulder. The ring is uniformly concentric with housing and shaft.
Ring groove
C o u p l e r a n d Ring
Shaft
Retaining ring
Coupling ha!f
Shaft
Coupling half
Retaining ring
H\t\q groove
Couplings locked to shafts •with set screw and keys
Where attractive appearance is desired in a dependable locking device, this connector and ring can be used.
Copyright © 2005 by The McGraw-Hill Companies
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Slotted Sleeve with Tapered Threads Retan in i g ring
Tapered threads
Sleeve
Co py rig hte dM ate ria l
Shaft
Collar
Slot
Add flat washer for better contact
A slotted sieeve with tapered threads connects shafts which cannot be machined Prongs on the retaining ring provide positive shaft gripping to stop collar movement The arched rim adds extra strength.
Bossed Coupling and ijngs Coupling half
Seam
Shaft
Shaft
Retaining ring
An alternate solution for coupling unmachined shafts uses bossed coupling halves with locking retaining rings.
Copyright © 2005 by The McGraw-Hill Companies
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T h e
V e r s a t i l e
R e t a i n i n g
R i n g
A design roundup of some unusual applications of retaining rings.
Co py rig hte dM ate ria l
Robert O. Parmley
SHAFT
GEAR
RETAINING RING
Fig 1 The assembly of a hubless gear and threaded shaft may be accomplished by using a "triangular nut retaining component which eliminates the need for a Jarge standard nut and lock washer or other spring type part. The dished body of the triangular nut flattens under torque to lock the gear to the shaft.
Excerpted from Assembly Engineering, February 1968 © Business News Media, Troy, MI, USA Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Co py rig hte dM ate ria l
Xivery engineer is familiar with the use of retaining rings in product assembly. Applications for this type of fastening device range from miniature electronic assemblies to heavy duty equipment. In spite of this widespread use, many opportunities for taking advantage of these versatile fastening components often are overlooked. However, when a value engineering approach is taken and the basic function of retaining rings as easily assembled locating and locking devices is kept clearly in mind it will be found that these simple fasteners can provide a unique solution to difficult assembly problems. This roundup of 8 unusual applications illustrates how different types of retaining rings have been used to simplify assembly and reduce manufacturing costs. The captions under the drawings give the details involved in each case. The author wishes to acknowledge with appreciation the cooperation he received from the Truarc Retaining Rings Division of Waldes Kohinoor, Inc. in developing these assembly designs.
SHAFT
GEAR AAINJATURE HIGH-STRENGTH RETAINING RING
KEY
Fig 2 This heavy duty hubless gear and shaft is designed for high torque and end thrusts. The retaining ring seated in a square groove and the key in slot provide a tamperproof lock. This design is recommended for permanent assemblies in which the ring may be subjected to heavy loads from either or both axial directions. An angled groove can be provided which has one wall cut at a 40° angle to the shaft axis. This will permit the ring to be repnoved without damage.
Fig 3 Two different types of retaining rings are used in this application involving a leaf spring and shackle assembly. A locking-prong retaining ring is bowed for tension while the prongs act as fastening elements to secure the pivot bolt. A flat or standard external ring is used as a flange or bolt head.
FRAME
FLAT RETAINfNG RING
SHACKLE
GROMME}
LEAF SPRING RING GROOVES LOCKING-PRONG RETAINING RING
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l
FLOAT
SEC,
A-A
•FLOAT ACTION
FLOAT GUlDEROD
SELF-LOCKING RETAINING RING
Fig 4 The self-locking retaining rings used in this application provide stops for a float. The rings are adjustable on the guide rod and yet the friction force produced by the heavy spring pressure makes axial displacement from the light weight hollow float impossible.
(ADJUSTABLE)
RING AFTER ASS*M.
FREE RING
Fig 5 Retaining rings provide a uniform circular shoulder for small diameter parts such as the pipe nipple shown here. In this case the retaining ring shoulder is used as a stop for the plastic tube. The wall thickness of the nipple should be at least three times as thick as the depth of the groove. When assembling the ring in the groove, the nipple should be supported by inserting a mandrel or rod.
GROOVE DETAIL
PERMANENT-SHOULDER RETAINING RING CONNECTION •NIPPLE
PLASTIC TUBING
MOISTURE JAR
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Fig 6 This internal retaining ring is a key part in the assembly of a connecting rod and piston for a hydraulic motor. The ring's lug holes make rapid assembly and disassembly possible when the proper pliers are used. The piston assembly in this case is slow moving and is not subject to heavy cycle loading.
CONNECTING ROD
PISTON
PISTON ASSVM.
Co py rig hte dM ate ria l
Fig 7 Internal self-locking rings can act as a support carrier when the I.D. of a sleeve or housing cylinder is too large to center and stabilize small rods or conduit. The rings are adjustable in the entry direction only, however, and a sufficient number should be used to secure the rod.
PISTON
$ EC. "A-A"
RETAINING RING
ADJUSTMENT
DiRECTiON
CONNECTING. ROD
-HOUSING CYCLINOER
FREE RlHG
(POD)
,KING
ROD
WASHERS
SLiDf STRAP CLAMP
I N T E R N A L .SELF-LOCKING RETAINING RING
Fig 8 The heavy duty external retaining ring shown here controls the elevation or position of a support post in a holding clamp. This type of ring is ideal for heavy duty applications where extreme loading conditions are encountered. By adding washers under the ring the elevation of the support post can be adjusted as required.
HEAVY-DUTY RN IG ENLARGEMENT
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
T h e
M u l t i p l e - P u r p o s e
R e t a i n i n g
R i n g
A roundup of ten unusual ways for putting retaining rings to work in assembly jobs. Robert O. Parmley
Retaining Ring Radius Arm Hub
Offset
Retaining Ring
Co py rig hte dM ate ria l
Retaining Ring
Panel Section
Insulation Cap
Shaft
Hub Centerline
1 p ecaio ls u lgs eu lh sss n rio gh o fs e xe tc ra ne an le y tS e i e d t o f e t tS r-h n io ljap e f a t f w c i h s i s t o i t n n tirle ry o r r o a t n i t g s o l w y l n i h u b cartf Cene urna.l Hose Hanger
Contact Point
2 B o w edasfcn rirga v tih /itrc o lcekp n iu g po rb n gd s a c 3 t f s e t n n g l m e n t a n s p n r i g e e l c i a l s h u -t tcn. Retaining Ring
Piece of Wire
Slot
Hydraulic Hose
Panel
Rod or Wire Support
Stem and Guide Rod
Retaining Ring
Wire Hook
Retaining RmR
Flat Washer
Tapered Coil Spring
3 S a ttind ah rdcolp e x e trnay t-llap epo n rirargcstc w h s n i u g s f po e ilslre,ass e m b y l r o v d i e i a h a n g e r o r s u p p o t r o f r h rods, and wre is.
Retaining Ring
Rods or Wires
Movable Head
4 S e o ld -flckn ia g ebe xlflatetrns aw lo n rlie g s irprou e w h t i a s h e r o t ics v d e d u j s a t h u d r o f onrtol of spn rig aco itn. Work Piece
Retaining Ring
Retaining Ring
Toe Clamp
Retaining Ring
Plate
Load
5 S e o l-jfls ca kb n ip gos e x e telo rnfalhea n rig gero ca orn -n ta ra o s l o i t i n y e r d i a n d u t e l c a b n rngemen.t
Eye Rod
Cable
Clamp
C am lp F arme 6 esavp yd -.us ytu l-fo cn kn igsw n rn iig a tH tdseo g re pn ich can lim Flat Washer
Excerpted from Assembly Engineering, July 1966 © Business News Media, Troy, MI, USA Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Retaining Ring
Stud
Pivot Pin
Post
Co py rig hte dM ate ria l
Adjustment
Platform
Retaining Ring
Retaining Ring
Supported Plate
Load
Alternate Grooves
7atndad S rras erxtea rn ao -ty lia p es n rs io g s e v r e s d u j s t b e l t ph orThe s h o u d l e o f p o s i t n n i g e l e v e m e m b e s r o n p o s t o r s a f t . p ostatiseflrea iin olckerd th te base by ts n ig n ig.o
Retaining Ring
Rea tn in ig R nig Be ad d as ls T ue b nigG
8 H e avyasasduy td s eo l-fltrckn is g n ro irn go a c s t a u j s a t b e o t p i u s e d s u p p o m e m b e frpn pale t seco itn. Retaining Ring
Steel Pin
Base
Base
tn in ighouR iggo Rea tn in ig R nigR s (eate n ia n sn ig rove) Houn sig
Rea tn in ig R nig
9 n Is e tv o rlec k n iug ethxateo rn ain lsrn ieg g e r s a s a l c k n g l m o f-r a c o p n i l g t o j i a lssentu tb n ig seco itns.
Adjustable
10 n Io tru e o rln kn eru x e t r n a l n r i g o l c k s w ta o p -c ed ic eigaho s n i g t h a t f i t s oa tn itg shaft.
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Roa n titg Shatf
Seam
M o r e
W o r k
f o r
R o u n d
R e t a i n i n g
R i n g s
Try this low-cost fastener for locking shafts and other parts. It will also work as a shaft step for bearings and an actuating ring for switches.
Co py rig hte dM ate ria l
Dominic J. Lalera
Set screw
Piston-
Conicof wedge. Spring-fingered cage Shaft
Rod*
Unfocked position
Ring,
Ring
Locked position
LOCK A SHAFT by forcing a retaining ring over the groove in the shaft. In locking position, the spring-fingered cage is actuated by the conical wedge.
PISTON IS LOCKED in place on the rod when drawn into place by means of a setscrew. To remove, slide the piston away from the ring, then remove the ring.
Section A-A Pipe Ring
Wire is threaded Ring into grooves
A
Shaft step -Ring
Flange Pipe
A;
FLANGE ASSEMBLY is permanently fastened by threading the wire into the mating grooves through the flange. Mange can rotate if wire doesn't protrude.
Copyright © 2005 by The McGraw-Hill Companies
THIS SHAFT STEP for a rotating bearing is quickly and simply made by grooving the shaft to accept a spring ring. Countcrbore the shaft step to mate.
Retrieved from: www.knovel.com
Co py rig hte dM ate ria l
Retainer plate'
Locking block. Cylinder wall
Ring*
Seal
'Ring
Cylinder head
THIS SPRING-HELD shaft lock is a basic application for retaining rings. The best groove dimensions for round spring rings are readily available from suppliers.
Switch mounting-bar Switch
Switch plunger
ASSEMBLE CYLINDER HEADS and similar parts to thin walls by means of a retaining ring and a locking block. Tightening the screws expands the ring.
Mate threaded wedge Internal wedge-
Ring
Actuating ring-
SWITCH ACTUATORS of round retaining rings offer a simple solution when permanent shaft steps would present assembly problems. Close the ring gap.
Copyright © 2005 by The McGraw-Hill Companies
THREE-PIECE WEDGE lets the shaft move freely until the wedge is tightened by screwing it in. The round retaining rirtg is then forced into the groove.
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D e f l e c t i o n s C i r c u l a r
o f
P e r p e n d i c u l a r l y
L o a d e d
S p l i t
R i n g s
M. M. Lemcoe
/ is the polar moment of inertia of a cross-section, the formula is
Co py rig hte dM ate ria l
FORMULAS FOR THE DEFLECTION of a split uniform circular ring perpendicular to the plane of the ring are given for various positions of the load. Methods of developing those formulas are demonstrated, In Fig. 1 is shown a split uniform circular ring of radius R, loaded with a force P applied perpendicular to the plane of the ring at the point B. At the point Q, the bending moment M and the twisting moment T due to the load P are respectively:
(D (2) Also, if there were a unit load at the point A, there would be at point Q a bending moment m and a twisting moment / due to that unit load. These are given by the following formula
(5)
The angle equals the smaller of angles a or fi. Substituting Eqs ( 1 ) , ( 2 ) , ( 3 ) and ( 4 ) into Eq ( 5 ) gives:
From the trigonometric identities sin (a - B) sin (0 - 0) =* $ [cos (a - 0) — cos (a + /9 - 20)] cos (a - 6) cos (/3 - 6) = \ [cos (a - 0) + cos (a + £ - 20)] The formula for A becomes:
(3) (4) From strain energy considerations, the deflection A of the point A can be formulated. If E is the modulus of elasticity and G is the shear modulus and if / is the moment of inertia about the neutral axis of a cross-section, and Fig. 1—Split circular ring loaded by a force perpendicular to the ring at point B. The deflection A at point A is to be calculated.
(6)
Integrating Eq ( 6 ) gives
(7)
Frorri Eq ( 7 ) formulas can be developed for A for various positions of points A and B. Formulas for various positions of points A and B are given below.
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
= = = =
Deflection at Point A Load at Point B Radius of Ring Modulus of Elasticity
G= Shear Modulus J = Cross-Section Polar Moment of Inertia I = Cross-Section Polar Moment of Inertia About Neutral Axis
Co py rig hte dM ate ria l
A P R E
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
I m p r o v e
D e s i g n
w i t h
R e t a i n i n g
R i n g s
Co py rig hte dM ate ria l
Waldes Kohinoor supplied the rings for the assembly illustrated here. Look at the old design, look at the new design. What did retaining rings do? Well, by changing the design to retaining rings these advantages are achieved: 1) Six beveled rings—one at each end of the three shaft bores—replace 24 hex-head bolts and eliminate drilling and tapping 24 holes in the cast housing. 2) Special gaskets needed to provide a proper seal between the end cap and housing have been replaced by less expensive standard O-rings. Six facing operations on the outside of the casting, required for the gasket seals, have been eliminated. (O-ring grooves are an integral part of the redesigned cover plates.) 3) Twelve external rings—six bowed, six flat—secure the inner races of the bearings. The rings are assembled in grooves machined simultaneously with the shaft cut-off and chamfering operations. They replace six threaded ring nuts and six lock washers and eliminate 12 ground diameters, six threading operations and six keyways on the shaft. 4) Six basic internal rings, installed in grooves machined in the housing, eliminate six machined shoulders and the need for holding close axial tolerances on the bearing bore and end cap. Reusable following disassembly, the rings are assembled with special pliers, and can be removed for field service.
End cop
OLD DESIGN
Beveled ring Lock washer End cop in keywoy
internal ring
Bowed ring
External ring
Nut Gasket
NEW OESiGN
O-ring
Courtesy: Machine Design: © Penton Media, Inc. Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION
19
Co py rig hte dM ate ria l
BALLS 12 Ways to Put Bas l to Work How Soft Bas l Can Sm i pfiy l Desg in Rubber Bas l Fn id Many Jobs Mutlp ie l Use of Bas l in Mk li Transfer Syse tm Use of Bas l in Reo ladn ig Press Nn ie Types of Bal Sd iles for Ln iear Moo tin Stress on a Bearn ig Bal Compact Bal Transfer Untis Ca lssc i Uses of Bas l in Vav les
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
19-2 19-4 19-6 19-8
19-10 19-12 19-14 19-16 19-17
1 2
W a y s
t o
P u t
B a l l s
t o
W o r k
Bearings, detents, valves, axial movements, clamps and other devices can all have a ball as their key element.
Co py rig hte dM ate ria l
Louis Dodge
^s provideJaterdUacafion
Dimple
DETENTPDWERDEPENDS 0NSPmNGSTRENGTHANDDlMPLEbEPTH, I
BALL-BEARING MACHINE WAY HAS Lj)W FRICTION.
Maximum recommended swing apg/e
BgL'Ma;.slightly'larger\thdn bore
Mvxfaium pifssipm swing tikgfe
Bin.
BALL ACCURATELY FINISHES BUSHING BORE.
BALL SHAFT |Np LETS !SHAFT SWING.
Clomping, force \
Double pafM bdlarice \ \ torque \
CLUTCH HAS LIMITED TORQUE TRANSMISSION.
Copyright © 2005 by The McGraw-Hill Companies
CLAMP UNEVEN WORKPIECES.
Retrieved from: www.knovel.com
Co py rig hte dM ate ria l
Backstop
Section A-Ai
CflECK VALVEJB^
IRAHSIVE^^
£nd\ clamped Men forced, dyer boll
Hdrd^ned pfafes \
THRUST-BEARING TAKES LIGHT LOADS.
BALL-LOCK FASTENS StUDJ IK MM WOLE . Expands wtieri htipdh is screwed orisiiofi\ Handle
rehaie hinge halves JBALL-LOOK SECURESHHANDUE TO SHAFT!
Copyright © 2005 by The McGraw-Hill Companies
(HIRGt PjN 1$ SEPARABLE.
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H o w
S o f t
B a l l s
C a n
S i m p l i f y
D e s i g n
Balls of flexible material can perform as latches, stops for index disks, inexpensive valves and buffers for compression springs.
Co py rig hte dM ate ria l
Robert O. Parmley
Anchor^ /to/esr
WbMrW)J
Adhesfye^ %ond I
W0fjp/?\ SprM
Sprfog Made
№/& &&M
Crip ikdirtfdftoft
Aj
l(ofy 0lkcompte$sf6H
hony I
ijisiji^
£Q|LEft AHH MHlJR flORjBAJiju3ilj „
iprpgr
~e№&~~
fid^tiSMlh
M
VnmpWein
ktwt '
J S ^
MQfJ$J&..
MWn
BW
CMamheA
VqcSum
. .„ * ,.JL..,. JL,_J ™ L,. ™L™~s L ;
Copyright © 2005 by The McGraw-Hill Companies
eteet
F1N(*R*etUAjrElJ RfertFiftttf
Retrieved from: www.knovel.com
l
tfofaflm
,L
(pU^Ma.m^L \rofahtdSfsJtl
(compress when instilling} Op№
e/i>s&f
Co py rig hte dM ate ria l
Open area
P
ftoffom ptastik MM
Chomfyen wall I !
CHEOKVALVi BAtt ISiPERMPENTtY INSTftl^LEEI B/MetJm/l:
MMM:
Pwb~po&
-SfRING BtHfFEfrf pCOMFRESSIOJ* SfRtN&l
Threaded end \
BhJl
PMiertd view
Alternate [design
Thhming
^ewrsefafy
f^b4rhHi
TWO-WAYM^^^
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
R u b b e r
B a l l s
F i n d
M a n y
J o b s
Plastic and rubber balls, whether solid or hollow, can find a variety of important applications in many designs.
Co py rig hte dM ate ria l
Robert O. Parmley
MailwMbkcokemM:
tyrohg
St&ppin
Wrong
Air tube
-Too krde LD. I
Leakage
ProiytimafMlvw ball valve
№ve4N
WallUhickwsSrA
Right
Wse
Ball mold seam
r;
AitjteM
eommcttoA
Not more tn)on\2t\
Altgmftg block \
Right
MOLD SEAMS on solid balls should bo held normal to flow line to avoid incom* plete seating and consequent leakage. j {
CENTRIFUGALLY MOLDED SPHERES can bo used in effN cient, Ioj*v-cost| sealing vjalvesy but avoid ball distortion by making .siltCL^itha^e^ciDn^ect dimensions are applied, I I \ \
Delicate finish
tigfrt tyokk pressure
Guidepin
Pressure post
Work piece
/ftibber-Mi
Retaining coUar
Adhesive bond
Rubber bail-
Base
Work piece
ALIGN DELICATE WORKPIECES on rubber balls that are bonded into base pillars. Adequate protection of fine finishes i s provided, while at the same time friction provides firm grip.
Copyright © 2005 by The McGraw-Hill Companies
Connection screws
VERTICAL PRESSURE-POST holds solid ball in easily removed retaining collar. Ball is solid and protects workpiece finishes during assembly operations.
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Co py rig hte dM ate ria l Washer*
Liy^ocHpth
Coil spring
Retaining.. wire\
dct{onxPl$te\
fhibttertiail'
"Ffcke
LocHhuf\
fSSeX
dosed
Bak
Bait
Opened
CUSHION PAD AND SHOCK ABSORBER is easily made for mounting-plates that must either carry dynamic loads or absorb shock forces.
BpTtffr&p&trt
DISCHARGE VALVE as shown here is an eftective way of controlling liquid displacement af the end of hoses wjjere,suction woijlclhe uuwjan|ed 0r harhifu1«
Guide sfeeve
Adh$s№
Bali
Rubber\baii bonded with adhekive "
FiWMe
Hoilow shaft
^wfngtjdl orpioh \
Bait
Afign holes
Stop Up
Moid hofe (optional)
HOLLOW SHAFT-SEAL embodies adhesive-bonded rubber ball with flow hole. Quick connection of leakproof joint for lubricant or other liquid is gained.
Pt vof pin
BUMPER STOP Is another example of thesimple buf effective] way a rubber ball can be employed to protect surfaces or partsq
Copyright © 2005 by The McGraw-Hill Companies
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M u l t i p l e i n
M i l k
U s e
o f
T r a n s f e r
B a l l s S y s t e m
Co py rig hte dM ate ria l
Source: Bender Machine Works, Inc. Illustrated by: Robert O. Parmley
Conveying
M i l k
Diagram
T r a n s f e r
S y s t e m
Washing
Copyright © 2005 by The McGraw-Hill Companies
A s s e m b l y
Diagram
Retrieved from: www.knovel.com
Front View
VACUUM LINE TUBE
TO FLEXIBLE UNE FOR TRANSFER SYSTEM (5/8 \D. TUBING)
Co py rig hte dM ate ria l
Ball
67 (ALTERNATE ELBOW ^ ADAPTOR)
WASHER — RELEASER j
ASER
Ball
ON OFF
Exploded View
Ball
DISCHARGE
Front View
Ball
Four plastic balls, located at key positions within the system, act as positive check valves as they respond to the vacuum pulsations.
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Side View
U s e
o f
B a l l s
i n
R e l o a d i n g
P r e s s
Inventor: E. E. Lawrence Draftsman: R. O. Parmley
Figure 1
Co py rig hte dM ate ria l
Ball
Figure 2
Copyright © 2005 by The McGraw-Hill Companies
Ball
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Ball Figure 3
Co py rig hte dM ate ria l
Figure 4
Ball
Figure 5
Figure 6
Figure 8
Figure 7
Copyright © 2005 by The McGraw-Hill Companies
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Ball
N
i
n
f o r
e
T
y
p
e
L i n e a r
s
o f M
o
B a l l t
i
o
S l i d e s
n
Co py rig hte dM ate ria l
Moving slide
Base
Adjusting screw
I
V grooves and flat surface make simple horizontal ball slide for reciprocating motion where no side forces are present and a heavy slide is required to keep balls in continuous contact. Ball cage insures proper spacing of balls; contacting surfaces are hardened and lapped.
Movable slide
Moving siide
2
Double V grooves are necessary where slide is in vertical position or when transverse loads are present. Screw adjustment or spring force is required to minimize looseness in the slide. Metal-to-metal contact between the balls and grooves insure accurate motion.
Load equalizing point
Movable slide
Path of boils
Load is shared by bails contacting hardened ways
(A) Holds siide securely but angle is more difficult to nnachine
(A)
Movable siide
Movable slide
Eccentric stud for adjustment.
Base
(B) Simpler construction, but requires additional bearing for twisting loads
(B)
3
BaIl cartridge has advantage of unlimited travel since balls are free to recirculate. Cartridges are best suited for vertical loads. (A) Where lateral restraint is also required, this type is used with a side preload. (B) For flat surfaces cartridge is easily adjusted.
Copyright © 2005 by The McGraw-Hill Companies
Ball bearings
J Commercial ball bearings can be used to make * a reciprocating slide. Adjustments are necessary to prevent looseness of the slide. (A) Slide with beveled ends, (B) Rectangular-shaped slide.
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Co py rig hte dM ate ria l Hardened §leeve
5
Sleeve bearing consisting of a hardened sleeve, balls and retainer, can be used for reciprocating as well as oscillating motion. Travel is limited similar to that of Fig. 6. This type can withstand transverse loads in any direction.
6
BaIl reciprocating bearing is designed for rotating, reciprocating or oscillating motion. Formed-wire retainer holds balls in a helical path. Stroke is about equal to twice the difference between outer sleeve and retainer length.
Snap-ring grooves simplify assembly
7
BaIl bushing with several recirculating systems of balls permit unlimited linear travel. Very compact, this bushing simply requires a bored hole for installation. For maximum load capacity a hardened shaft should be used.
8
Cylindrical shafts can be held by commercial ball bearings which are assembled to make a guide. These bearings must be held tightly against shaft to prevent looseness.
9
Curvilinear motion in a plane is possible with this device when the radius of curvature is large. However, uniform spacing between grooves is important. Circular - sectioned grooves decrease contact stresses.
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
S t r e s s
o n
a
B e a r i n g
B a l l
These curves indicate permissible loads when seat is spherical or flat, steel or aluminum.
Co py rig hte dM ate ria l
Jerome E. Ruzicka
COMPRESSV I E STRESS FOR STEEL BALL ON STEEL SEAT (For au l mn i um seat, multiply stress by 0.632)
N- 5-- p- for curved seat;
Stf6SS Ol33 fomDrPSciwp cstress, n<;ixlOOoIforfor tenSile ™ltiplybyby 03| Compressive trP« psixlOOO| sheQr stres^ ' mu(tjp[y
jf for flat seat
When a design uses steel bearing balls to support a load, it is important to know what stresses result. They are charted on this page. On the continuing page is a diagram that identifies symbols—for applications where the seat is spherical or flat—and also a chart that will help calculate maximum permissible loads.
Compressvi e load, P, Ib
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Symbols used with curves
Battradius,
Confochorea radius, r
Co py rig hte dM ate ria l
Sphericof seat radius,
Compressive toads
Contact radius, in. (r)
CONTACT RADIUS FOR STEEL BALL ON STEEL SEAT (For aluminum seat, multiply radius by 1.25)
N values, in.'1
For non-permanent surface deformation; Pmgx
Compressive load FJ Ib
Copyright © 2005 by The McGraw-Hill Companies
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o
m
p
a
c
t
B a l l
T r a n s f e r
U n i t s
Co py rig hte dM ate ria l
C
Masses of ball transfer units in airplane floor make it easy to shove cargo loads in any direction.
An improved design of an oftneglected device for moving loads— ball transfers—is opening up new applications in air cargo planes (photo above) and other materials handling jobs. It can serve in production lines to transfer sheets, tubes, bars, and parts. Uses of established ball transfer units have been limited largely to furniture (in place of casters) and other prosaic duties. With new design that takes fuller advantage of their multiple-axis translation and instantaneous change of direction, ball transfer units can be realistically considered as another basic type of anti-friction bearing. The improved
units are made by General Bearing Co., West Nyack, N.Y. How they work. Essentially, ball transfers (photo below) are devices that translate omnidirectional linear motion into rolling motion to provide an unlimited number of axes of movement in any given plane. In such a unit, a large main ball rotates on its own center within a housing. This ball is supported by a circular group of smaller balls (drawing below) that roll under load and, in so doing, recirculate within the housing in endless chains. These units are designed either as "ball up" or as "ball down." In the "ball down" units, design must pro-
vide a positive means of recirculating the support balls so they won't fall away under their own weight. Variations. Many different configurations are available to suit the specific requirements of customers. Balls of carbon steel are most often used, but stainless steel balls are available for uses where corrosion may be a problem. Ball transfer units can be sealed to exclude dirt. Where loads require that a number of ball transfers must simultaneously contact the load surface, a spring technique has been developed. Each ball transfer (drawing below) is spring-loaded. It starts to deflect when its own rated load is exceeded, allowing other ball transfers to pick up their share of the load. This concept also provides protection against major overloads in any ball transfer unit. D
Main ball shown, 1 in. did., is supported by 70 smaller balls, hidden.
Shaded area seen from above shows load; arrows show ball circulation.
Spring loading assures even distribution of the load on the small balls.
C o m p a c t
ball
roll
e v e r y
l o a d s
t r a n s f e r
w h i c h
u n i t s w a y
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
C l a s s i c
U s e s
o f
B a l l s
i n
V a l v e s
Co py rig hte dM ate ria l
OUTLET
BALL FLOAT
INLET
OUTLET
AIR
RELEASE
VALVE
BALLFLOAT
INLET C O M B I N A T I O N AIR
VALVE
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
OUTLET
Co py rig hte dM ate ria l
B A L L FLOAT
NEGATIVE
PRESSURE
VALVE
BALL
FLOAT
OUTLET
INLET
WASTEWATER
AIR
R E L E A S E
VALVE
BALL
FLOAT
INLET
VACUUM
Copyright © 2005 by The McGraw-Hill Companies
BREAKER
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AIR
VALVE
Index
NOTE: Subjects are followed by double numbers to indicate each page reference. The (first) bold-face number indicates the section; the (second) light-face number is the page number of that section.
Index terms
Index terms
Links
small
20-8
stress
19-14
unusual applications
Links
20-8
Bellows
Action: mechanical
Bellows coupling
1-6
1-8
retaining rings
6-13
Axial motion
Backlash: eliminate limit-switch prevention threaded parts Balances
18-6
1-10
creep
9-10
drives
9-2
rubber slides soft transfer units
9-6
leather
9-16
length
9-4
valves Bead chains
9-16
1-18
tension
9-14
1-16
types
9-2
11-12
Bevel gears
2-9
water
Bolts
19-14
Bumpers
19-6
5-3
11-17
2-21 5-2 15-6
Bushings: (see Section 20)
19-12
19-4
19-16
19-17
flanged
20-2
rubber
20-5
tapered
5-15
20-5
8-8
C
19-14
Cams: (see Section 14)
cage
20-16
controlled system
lubrications
20-12
rotary-linear
6-6
Bike:
2-5
ball
rolling contact
6-4
9-4
speeds
Bearings: (see Section 20)
miniature
9-14
9-14
1-14
19-8
9-10
9-16
hybrid
open
Ball(s): (see Section 19) bearings
9-2
9-14
mechanisms
B
10-4
closed
horsepower loss
2-20
18-4
13-12
Belts: (see Section 9)
creative, (see Section 2) piping
16-12
Belting: (see Section 9)
13-6
Amplify mechanical movement Angular conversion
Belt drives
1-8
Adjustable springs
Assemblies:
7-9
Co py rig hte dM ate ria l
Belleville washers
A
20-14
20-14
20-8 20-10 20-7
curves
14-2
programmed motion
14-9
spherical
14-11
types
14-14
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14-16
Retrieved from: www.knovel.com
I-1
I-2
Index terms
Links
Index terms
Links
Cardan-gear mechanisms
6-25
tamper-proof
4-16
Centrifugal clutches
7-12
Control mountings
2-6
Chains: (see Section 8)
Control vault
bead
8-8
drives
8-10
history
8-2
lubrication
8-12
roller Clamps: friction spring Clinching
8-4
12-14
Crank
6-19
Crank slide
3-16
belt
flexible
5-6
fluid
2-15
5-18
novel
10-26
offset (shafts)
10-18
10-8
7-12
rotating (shafts)
10-14
7-16
small diameter (shafts)
10-12
7-19
universal
10-24
low-cost designs
7-8
Cupped washers
16-14
mechanical
7-2
one-way overriding overrunning roller-type serrated
Coiled pins
7-6
7-8
7-20
hubless gear fastening lanced metal
Deflection: (see Specific)
10-12 7-20 7-19
13-4
13-6
13-18
locking
5-6
retaining
5-6
serrated
7-16
Devices: (see, also, specific) indexing
12-17
Connections: (see Section 4)
hub fastening
7-18
Detents:
7-16
Compression springs
doweled
6-18
D
13-20
Diaphragms
1-11
Disc-clutch
7-19
Dished washers
4-20
4-8 4-2
Doweled fasteners
4-18
pin, (see Section 12) 4-2
spliced
18-8
splined
4-6
spring
4-12
1-12
3-13
16-10 4-8
4-18
Drives:
4-4
shafts
2-18
locking, (see Section 5)
Components: (see Specific)
circular
Cycloid gear mechanisms
7-4
torque capacity Coil springs
7-10
10-16
7-20
small-diameter (shafts) spring-loaded
10-22
Couplings: (see Section 10)
5-2
10-10
disc
10-20
9-10
parallel (shafts)
detents
12-21
Creep:
5-4
7-2
centrifugal
12-20
Creative assemblies: (see Section 2) 8-12
Clutches: (see Section 7) basic types
2-20
Co py rig hte dM ate ria l
Clamping device
Cotter pins
5-16
angle
9-2
belt
9-2
chain
8-10
epicycloid
6-21
Geneva light-duty locking, (see Section 5)
This page has been reformatted by Knovel to provide easier navigation. Copyright © 2005 by The McGraw-Hill Companies
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1-2 2-10
9-10
10-9
I-3
Index terms
Links
Index terms
Drives (Continued)
Links
Friction clamping
5-4
low-torque
1-4
mule
9-2
G
open
9-2
Gear-tooth
reverse
9-2
Gearing: (see Section 6)
serpentine
9-2
calculations
6-6
steel-tape
9-12
mechanisms
1-2
three-dimensional
3-14
systems
6-4
6-13
6-18
6-25
6-27
Co py rig hte dM ate ria l
worksheets
E
6-2
6-6
Gears: (see Section 6)
Elliptical slides Engine: rotary piston
13-16
2-2
alignment
6-8
bevel
2-9
calculations
6-6
Epicyclic gear trains
6-16
cardan
Epicycloid drives
6-21
connections (to shaft)
Extension spring
cycloid
13-16
dimensions
F
epicyclic
Face gears
6-8
Fasteners: (see, also, specific) bolted clinching doweled lanced metal polyethylene polystyrene sheet metal snap spring tamper-proof
11-10 4-8
sheet metal tamper-proof Fixture: holding Flanged bushings Flanged inserts
6-14 6-10
5-22
sets
6-14
sheet metal
8-14
5-18
spur
6-10
4-12
sun
6-14
4-16
systems
6-27
5-18
11-8
tooth
6-4
trains
6-16
worms
6-5
Geneva drive
1-2
Geneva wheel
1-1
4-20 5-20 4-16
Grooved pins: (12-18)
5-8
20-4
15-9
round-head
12-19
T-head
12-20
Grommets: (see Section 15)
13-22
13-24
Flat washers
16-2
16-4
16-6
10-18
10-20
10-22
Four-bar linkage
6-26
7-22
6-2
power capacity
Flat springs Flexible couplings
6-20
6-27
5-20
20-2
6-18
6-16
14-16
Fastening: (see, also, specific) circular parts
5-11
6-4
4-4
4-18
5-16
4-4
6-18
hubless
planetary
4-10
4-2
6-8
nomenclature
5-18
6-25
face
lubrication
11-11
6-6
inserts
15-4
rubber
15-2
3-22
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6-13
6-19
14-8
I-4
Index terms
Links
Index terms
H
Links
Limit-switch
Helical gears
6-2
Helical wire inserts
6-4
Linear motion: (see specific)
15-15
Hook’s joint
1-18
Linkage: (see Section 3)
3-15
Horsepower: (see, also, specific)
applications
3-22
four-bar
3-22
loss
9-16
industrial
3-22
speed
9-16
linear strokes
3-10
4-2
novel
Hubless fastening
4-4
power thrust
9-6
push-pull
2-4
shafts
10-8
short motion
3-12
Hybrid belts Hydraulic motor Hydrometer
I Idler Index error Indexing
1-9
7-8
straight-line motion
9-2
6-13 2-18
spacers threaded wire
Interlocking fastening
J
Keyhole Keys
L
15-4
15-8
15-12
3-18
toggle
3-20
torque
10-6 5-4
5-18
5-2
clamps
5-6
11-8
5-8
friction
5-2
locking detents
5-4
11-10
mountings
5-14
sheet metal
5-19
snaps
5-18
threaded
10-12
5-18
fixture
methods
5-14
11-10
clamping clinching
15-15
Low-torque drives
11-16 1-4
Lubrication:
Leather belts
9-16
Light-duty drives
thrust
3-6
Locking devices: (see Section 5)
15-10
4-18
Lift station
3-14
methods
15-9
Lanced metal fasteners Levers
3-4
devices (see Section 5)
Joints: (see specific)
K
3-2
three-dimensional
detents
Inserts: (see Section 15) metal
3-18
Locking:
Ingenious mechanisms: (see Section 1) flanged
10-26
Co py rig hte dM ate ria l
Hub fastening
1-6 2-6 13-10 2-20
bearings
1-7 3-9
1-8 13-3
20-12
chains
8-12
gears
6-27
20-14
M Mechanical:
8-8
action
1-8
clutches
7-2
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7-10
3-8
I-5
Index terms
Links
Index terms
Mechanical (Continued) movement
1-6
2-18
belt drives
9-2
9-14
cardan-gear
6-25
cycloid gear
6-18
hypocycloid
6-18
Mechanisms: (see Section 1)
saw-matic
2-19
Metal inserts
Milk transfer system Miniature bearings
Modified Geneva drives Motion: axial linear mechanical rotational Motor: hydraulic Mounting units
Overload prevention
2-12
Overriding clutches
7-4
Overriding spring mechanisms
1-4
Overrunning clutches
7-6
Pinion
Mushroom bumpers
1-2 1-4
13-24
19-8
20-8
gears Nuts
1-10
19-12
6-3
12-21
grooved
12-18
12-19
grooved T-head
12-20 12-16
12-12
strength
Piping assembly
20-10
12-2
spiral-wrapped
spring-loaded
2-4
4-5
12-10
spring
1-8
4-4
split
1-10
12-4
12-6
12-16
12-17
12-20
12-8
7-20
12-22 2-20
Planetary gears:
15-6
systems
Pneumatic spring
6-2
2-6
2-8
6-2 8-14
12-14
sets
Nomenclature:
1-16
cotter
cam-controlled
N
1-7 3-18 6-8
12-17
slotted spring
2-4
7-18
coiled
locking
1-2
1-6
7-8
Pins: (see Section 12)
13-22
15-10
2-3
2-14
10-10
Co py rig hte dM ate ria l 6-21
spring
8-20
Parallel shafts 1-4
parallel-guidance special
One-way drive
P
ingenious, (see Section 1) overriding
Links
11-2
11-10
Power thrust linkage Push-pull linkage
11-11
14-16 6-14
14-16
13-26 3-18 3-2
Q
O
Quick-release pins (see specific)
O-rings: (see Section 17) applications
17-2
17-4
17-12
recommendations
17-14
R
seals
17-16
Ratchets
Offset shafts
10-8
Oil: lubrication of bearings One-way clutch
20-12
20-14
3-20
7-3
7-8
8-14 8-20
8-16
8-18
Reducers: speed
7-20
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2-8 15-9
19-10
I-6
Index terms
Links
Index terms
Retaining rings: (see Section 18) assembly
8-4
circular
8-6
18-20
Links
coupling
10-2
critical speeds
10-5
end supports
10-5
18-8
comparisons
18-2
equal strength, (pin vs. shaft)
10-6
12-22
coupling shafts
18-8
fastening
10-8
10-10
linkage
10-8
14-11
offset
10-8
overview
10-2
loaded split circular locking
4-3
versatility
18-16 5-13
parallel
18-12
Rings, (see specific) Roller chain
10-10
Co py rig hte dM ate ria l
multiple-purpose tapered
18-20
rectangular
10-7
rotation
2-16
small-diameter
8-4
10-12
7-20
square
10-7
Rotary liner bearings
20-7
tapered
5-15
Rotary motion
1-10
universal
Roller-type clutch
Rotary piston engine Rotary shafts Rubber balls Rubber bushing Rubber grommets Rubber washers
S
10-14 20-5 15-2 16-6
2-19
Screw thread
11-4
alignment applications arrangements self-locking Seals: o-ring pump valve
Self-locking screws SEM: applications
8-14
11-16
clinching
5-20
interlocking
5-18
snaps
5-22
Shock control
2-6
Short-line linkage
3-4
Slotted pins
12-2
12-16
Snap-action fasteners
5-22
5-24
Snap fasteners
5-18
5-20
11-4
Space crank
3-17
Spacers: (see Section 15)
11-16
17-16
adjustable
15-4
jig & fixture
15-8
mushroom
15-6
17-16
Speed reducers
2-8
11-16
Spherical cams
14-11
Spider
11-20
16-16
14-8
Spiral-wrapped pins
12-12
Splined connections
4-6
standards
16-17
Serated clutches
7-16
Split hub
4-3
Serated washers
16-8
Split pins
12-10
Shafts: (see Section 10) connections
4-2 10-2
4-4 10-8
4-6
3-6
3-12
Snap rings, (see specific)
11-14
5-24
Short-motion linkage
11-8
17-14
10-24
Sheet-metal fastening: 5-20
10-16
19-6
Saw-matic mechanism Screws:
Sheet-metal gears
2-2
10-12
Sprags
7-20
Spring bands
7-18
Spring clamps
5-8
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3-8
5-22
I-7
Index terms
Links
Spring-loaded pins
7-20
Spring lock washer
11-11
Spring pins
12-2
Spring washers
5-15
Index terms Toggle press
13-18
Belleville
13-12
16-12
compression connections detents extension flat helical wire lever mechanisms pneumatic stiffeners Sprockets
13-4
13-6
13-18
13-20
5-6
13-16
13-22
Universal shaft couplings
13-8
13-10
13-12
8-20
arrangements inserts screws
6-26
7-22
6-4
6-13
self-locking Threaded members
2-20
lift station
2-20
16-12
cupped
16-14
dished
16-10
flat
16-2
rubber
16-6
SEM applications
16-16
SEM standards
16-17 16-12
tapered
11-11
11-8
Water bike
2-21
11-4
Wheel:
Geneva
11-14
Wire inserts
15-12
11-4 11-16
11-8
Woodruff keys Worm gear Worms
5-2
Three-dimensional drive
3-14
Toggle linkage
3-20
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16-4
16-8
spring
11-16
19-17
2-6
Belleville
serrated
8-18
11-2 11-14
1-11
Washers: (see Section 16)
Threaded components: (see Section 11) applications
1-10
W
4-16
6-2
10-24
control
Vibration
12-19
6-14
3-15
Vault:
13-26
3-4
Tamper-proof fasteners
Valves
13-22
Straight-line motion
alignment
2-3
V
15-15
3-8
ratchets
6-16
13-24
3-6
gear
10-6
Universal joint
7-16
Straight-line linkage
Teeth:
limiting shaft
U
6-10
T
2-10
Transfer system
4-12
6-4
Sun gears
limiters
gear
8-15
Studs
7-19
Train:
13-20
8-14
Spur gears
disc-clutch
Co py rig hte dM ate ria l
coil
3-21
Torque:
Springs: (see Section 13) adjustments
Links
1-1
6-19
15-15 10-2 6-5 8-14
10-3
14-8
MACHINE DEVICES and COMPONENTS I L L U S T R A T E D
S O U R C E B O O K
SECTION 20
Co py rig hte dM ate ria l
BUSHINGS & BEARINGS
Gon ig Creatv ie wtih Falnged Bushn igs Seven Creatv ie d Ieas for Falnged Rubber Bushn igs Rotary-Ln iear Bearn igs Unusual Appc ilato ins of Mn ia iture Bearn igs Ron ilg Contact Bearn ig Mounn itg Untis Ee lven Ways to Oil Lubrc iate Bal Bearn igs Lubrc iato in of Smal Bearn igs Cage Keeps Bearn igs in Ln ie and Lubrc iated
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20-2 20-5 20-7 20-8 20-10 20-12 20-14 20-16
G o i n g
C r e a t i v e
w i t h
F l a n g e d
B u s h i n g s
These sintered bushings find a variety of jobs and are available in 88 sizes, from /s inch to 1 /8 inch internal diameter.
Co py rig hte dM ate ria l
Robert O. Parmley
PuIfey surfaces
Journal bushings
Shaft
Mating halves
{All drive fits)
Journal bushings
Lock bearings in place
Instant step-pulley
Slight compression
Clearance
Journal bushings
Journal bushing
Hanger bracket
Bolt
Frame
Leaf spring
Journal bushing
'Hinge holves
Removable hinge pin
Leaf-spring eye-bearings
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Co py rig hte dM ate ria l Coil spring
Mating halves
SlOt
Workpiece alignment
Press to release clevis
Table
Journal bushing
Post or location-pin holder
Slotted slide
Clevis
Spring-loaded pins
Action
Stem
Journal bushing I Press fit )
Journal bushing Seat plate Handle or knob
Slider pin is self-lubricating
Copyright © 2005 by The McGraw-Hill Companies
Journal bushing
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Co py rig hte dM ate ria l
Adjust spring tension-use long plunger Plastic or to set bushing, (press fit J rubber pipe Inserted plastic sleeve
Checkvalve
Boil
Coil spring
Journal bushing
Work piece,
Press fit Table
Holding fixture, complete with feet
Journal bushing
Cornering put
R
JournalSection A-A bushing, Pin
Twine
Journal bushing
Shelf
Pin
Base
Base
(Press fit in bose only)
Bobbin
Shelf post
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Typical shelf
Bench
S e v e n
C r e a t i v e
R u b b e r
I d e a s
f o r
F l a n g e d
B u s h i n g s
They're simple. Inexpensive, and often overlooked. Check your design for places where rubber bushings may be a solution to a design problem.
Co py rig hte dM ate ria l
Robert O. Parmley
Flanged rubber bushing
Coil spring
Conduct
Wires
Flat washers
Flanged, rubber bushing Axle
Press fit or adhesive
WeU
Flonged rubber bushing
Shock absorber
Conduit liner
p
Collar mount leg
Cylinder housing flanged rubber bushing Adhesive bond Valve rod
CoJI sprina
Flanged -rubber bushing,
To dose Concrete floor Anchor bolt
Valve seat
Spring support
Copyright © 2005 by The McGraw-Hill Companies
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Co py rig hte dM ate ria l Expansion screw
Thr~jed' insert
Wood
Ffijnged • rubber bushing.
So te no id
Brocket
Flanged rubber bushings
Seal expander
Cushion and noise absorber
Cioss
Connection
Hord rubber press fit
Metal
Piostic or rubber tube Adhesive bond Flonged rubber bushings Nipple connection
Copyright © 2005 by The McGraw-Hill Companies
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Mounting pfote
R o t a r y - L i n e a r
B e a r i n g s
Rotary-linear bearings can take a beating from heat and shock. New designs find first use in steel converter, where heat cause expansion and shaft and jarring blows are applied.
the making of steel, the trunnion bearings are subjected to severe punishment by the very hot, very heavy load. The shaft that supports the converter heats up and expands, causing the bearings to slide inside their housings. The wear caused by this action is bad enough. It means additional power is needed to overcome friction when the shaft is rotated during oxygen lancing operations. Worse yet, however, is the fact that when the sliding surfaces start to gall, the bearing will seize. One-sided. Only one of the pair of horizontal shafts supporting the converter is equipped with the new bearing assembly. This shaft and bearing take up the expansion. The other shaft is supported by a conventional trunnion bearing. Both bearings are packed with a
Co py rig hte dM ate ria l
A novel two-directional bearing designed especially for steelmaking equipment may find other uses where the loads are hot and heavy. In this design, a linear inclined bearing causes the bearing housing to roll over the roller bearings (sketch below, right) instead of sliding as in conventional designs. Because of its demonstrated reliability, this assembly of pillow block and bearing is already being used in steel mills throughout the country. It was designed by Carl L. Dellinger, an engineer with Norma-HofTmann Bearings Corp., Stamford, Conn., to overcome problems of friction along with thermal expansion. Hot, heavy load. The prime use of the new design is in the trunnion that supports a steel converter. When 250 tons of molten metal at 3200 F are poured into a converter during
lithium-based grease that contains molydisulflde and special extremepressure additives to operate in the 200 F temperature inside the bearing. The grease is held in the housing by a Buna N seal that keeps out contaminants. Heat and shock. As the shafts expand, the spherical roller bearing at the end of one shaft rolls over the enclosed and inclined linear-motion bearings. These linear bearings are tilted 20 deg. from the axis of the shaft center line. Dellinger found that if the lines normal to the roller axis are allowed to intersect above the shaft center line, the housing can withstand greater torsional loads. In the converter, severe torsional loads are produced during de-sculling operations (knocking out the cooled metal that adheres to the inside of the vessel after steel has been poured out). To remove this encrustation, the converter is rotated until it hits the base plate with the jarring impact of a truck hitting a brick wall. This shock load dislodges the steel, but it punishes the support bearings.
Spherica roller bearings
Seal
IV2 million Ib toad
Roller bearings
Spherical and linear motion bearings are contained in a sealed housing. The linear bearings are inclined for stability under torsional loading.
Copyright © 2005 by The McGraw-Hill Companies
Linear roller bearings take up thermal expansion of shaft and housing, to eliminate sliding.
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U n u s u a l o f
A p p l i c a t i o n s
M i n i a t u r e
B e a r i n g s
R. H. Carter
Housing
Co py rig hte dM ate ria l
Housing
Shaft
Fig. 1—BALL-BEARING SLIDES. Six miniature bearings accurately support a potentiometer shaft to give low-friction straight line motion. In each end housing, three bearings are located 120 deg radially apart to assure alignment and freedom from binding of the potentiometer shaft.
Bearings
Bearing
Cam
Pawi arm
Spring
Fig. 2—CAM-FOLLOWER ROLLER. Index pawl on a frequency selector switch uses bearing for a roller. Bearing is spring loaded against cam and extends life of unit by reducing cam wear. This also retains original accuracy in stroke of swing of the pawl arm.
Pivot point
Two pivot bearings back-toback
Fig. 3—SEAT FOR PIVOTS. Pivot-type bearings reduce friction in linkages especially when manually operated such as in pantographing mechanisms. Minimum backlash and maximum accuracy are obtained by adjusting the threaded pivot cones. Mechanism is used to support diamond stylus that scribes sight lines on the lenses of gunnery telescopes.
Adjustable pivot cones
Pivot bearing
Linkage
Linkage
Fig. 4—SHOCK-ABSORBING PIVOT POINT. Bearing with spherical seat resting on spring acts as a pivot point and also absorbs mild shock loads. Used on a recording potentiometer that is temperature controlled. Spring applies uniform load over short distances and gives uniform sensitivity to the heat-sensing element. Close fit of bearing in housing is required.
Copyright © 2005 by The McGraw-Hill Companies
Threaded housing for adjustments
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Spring
Clamp
Co py rig hte dM ate ria l
Bearing^
Fig. 5—PRECISE RADIAL ADJUSTMENTS obtained by rotating the eccentric shaft thus shifting location of bearing. Bearing has specialcontoured outer race with standard inner race. Application is to adjust a lens with grids for an aerial survey camera.
Eccentricity
Lens
Eccentric shaft
Thrust bearing
Flanged bearing
Threaded collar
Shaft
Stepped collar
Housing.
Gear train
Fig. 7—GEAR-REDUCTION UNIT. Space requirements reduced by having both input and output shafts at same end of unit. Output shaft is a cylinder with ring gears at each end. Cylinder rides in miniature ring bearings that have relative large inside diameters in comparison to the outside diameter.
Outer bearing race Inner bearing race.
Output shaft (cylinder) Bearing'
Fig. 6—SUPPORT FOR CANTILEVERED SHAFT obtained with combination of thrust and flanged bearings. Stepped collar provides seat for thrust bearing on the shaft but does not interfere with stationary race of thrust bearing when shaft is rotating.
Ring gear
Shaft Collar
Ring bearings Output gear Cylinder
Input gear
Rubber tip for tachometer readings
Input shaft Stationary housing
Copyright © 2005 by The McGraw-Hill Companies
Fi g . 8—BEARINGS USED AS GEARS. Manually operated tachometer must take readings up to 6000 rpm. A 10-to-l speed reduction was obtained by having two bearings function both as bearings and as a planetary gear system. Input shaft rotates the inner race of the inner bearings, causing the output shaft to rotate at the peripheral speed of the balls. Bearings are preloaded to prevent slippage between races and balls. Outer housing is held stationary. Pitch diameters and ball sizes must be carefully calculated to get correct speed reduction.
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R o l l i n g o
u
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t
i
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o
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t
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B
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U n i t s
FIG. I—Pillow blocks are for supporting shafts running parallel to the surface on which they are mounted. Provision for lubrication and sealing are incorporated in the pillow block unit. Assembly and disassembly are easily accomplished. For extremely precise installations, mounting units are inadvisable.
Co py rig hte dM ate ria l
M
C
FIG. 2—Pillow blocks can be designed to prevent the transmission of noise to the support. One design (A) consists of a bearing mounted in rubber. The rubber in turn is firmly supported by a steel casing. Another design (B) is made of synthetic rubber. Where extra rigidity is required the synthetic rubber mount can be reinforced by a steel strap bolted around it.
Rubber
(B)
(A;
FIG. 3—Changes in the temperature are accompanied by changes in the length of a shaft. To compensate for this change in length, the pillow block (B) supporting one end of the shaft is designed to allow the bearing to shift its position. The pillow block (A) at the other end should not allow for longitudinal motion.
Meld end
(A)
(B)
Ball bearing
Rotter bearing
(A)
(B)
Fig* 4—Compensation for misalignment can be incorporated into pillow blocks in various ways. One design
(C)
(A) uses a spherical outer surface of the outer race. Design (B) uses a two-part housing. The spherical joint
Copyright © 2005 by The McGraw-Hill Companies
compensates for misalignment. Another design (C) uses a spherical inner surface of the outer race.
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Co py rig hte dM ate ria l
Fig. 5—The cylindrical cartridge is readily adaptable to various types of machinery. It is fitted as a unit into a straight bored housing with a push fit. A shoulder in the housing is desirable but not essential. The advantages of a predesigned and preassembled unit found in pillow blocks also apply here.
FIG. 6—-The flange mounting unit is normally used when the machine frame is perpendicular to the shaft. The flange mounting unit can be assembled without performing the special boring operations required in the case of the cartridge. The unit is simply bolted into the housing when it is being installed.
FIG. 7—The flange cartridge unit projects into the housing and is bolted in place through the flange. The projection into the housing absorbs a large part of the bearing loads. A further use of the cylindrical surface is the location of the mounting unit relative to the housing.
Traise/
(A)
FIG. 8—Among specialized types of mounting units are (A) Eccentrics used particularly for cottonseed oil ma-
(B)
chinery and mechanical shakers and (B) Take-up units which make possible an adjustment in the position of
Copyright © 2005 by The McGraw-Hill Companies
the shaft for conveyor units. Many other types of special rolling contact bearing mounting units are made.
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E l e v e n B a l l
W a y s
t o
O i l
L u b r i c a t e
B e a r i n g s
D. L. Williams Fig. 1—Oil Level System,. For moderate speeds, the bearing housing should be filled with oil to the lowest point of the bearing inner race. An oil cup is located to maintain this supply level. Wick acts as a filter when fresh oil is added. This system requires periodic attention.
Co py rig hte dM ate ria l
The method by which oil should be applied to a ball bearing depends largely on the surface speed of the balls. Where ball speeds are low, the quantity of oil present is of little importance, provided it is sufficient. Over-lubrication at low speeds is not likely to cause any serious temperature rise. However, as speeds increase, fluid friction due to churning must be avoided. This is done by reducing the amount of oil supplied and by having good drainage from the housing. At very high speeds, with light loads, the oil supply can be limited to a very fine mist.
FIG 1
Shielded bearing
FlG 2
Fig. 5—Drop Feed. Oil may be fed in drops using either sight-feed oilers or an overhead reservoir and wick. Drains must be provided to remove excess oil. A short overflow standpipe, serves to maintain a proper oil level. It also retains a small amount of oil even though the reservoir should be empty.
FIG 3
Overflow pipe
FI64 Off metering holes'
Fig. 4—Spray Feed. With higher speeds, definite control of oil fed to bearings is important. This problem is more difficult for vertical bearings because of oil leakage. One method uses a tapered slinger to spray oil into the bearings. Oil flow is altered by the hole diam., the taper and oil viscosity.
Fig. 2—Splash Feed is used where rotating parts require oil for their own lubrication. Splash lubrication is not recommended for high speeds because of possible churning. Bearings should be protected from chips or other foreign material by using a shaft mounted slinger or shielded bearings.
Fig. 5—Circulating Feed. Most circulating systems are somewhat complicated and expensive but this is justified by their permanence and reliability. Oil reservoir is attached to the shaft and when rotated, the oil is forced upward where it strikes a scoop, flows through and onto the bearing. Oft fevef when
rotating
7ctpered slinger
FlG 5
Copyright © 2005 by The McGraw-Hill Companies
Stationary
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o/f tevef
Co py rig hte dM ate ria l
Fig. 7—Another screw pump application forces the oil upward through an external passage. The cup-shaped slinger traps some oil as the spindle comes to rest. Upon starting, this oil is thrown into the bearings and avoids a short initial period of operation with dry bearings.
FIG 7
Overflow drain
Oil slinger
FIG 6
Fig. 6—Most circulating systems are used for vertical shaft applications and usually where ball speeds are comparatively high. One system consists of an external screw which pumps the oil upward through the hollow spindle to a point above the top bearings.
Oil slinger
Oi/ reservoir
Oil reservoir
Fig. 8—Wick Feed filters and transfers oil to a smoothly finished and tapered rotating member which sprays a mist into bearings. Wick should be in light contact with the slinger or else the wick may become glazed or charred. A light spring is often used for proper wick pressure.
Oil slingers
FIG 9
FIG 10
Air1 oil misr
Wick FIG 8
Pressurized oil
Fig. 9—Wick feeds are used in applications of extremely high speeds with light loads and where a very small quantity of oil is required in the form of a fine mist. Slingers clamped on the outside tend to draw the mist through the bearings.
FIG 11
Oil return
Drainage holes Air
Oi! return
Fig. 10—Air-Oil Mist. Where the speeds are quite high and the bearing loads relatively light, the airoil mist system has proven successful in many applications. Very little oil is consumed and the air flow serves to cool bearings.
Copyright © 2005 by The McGraw-Hill Companies
Fig. 11—Pressure Jet. For high speeds and heavy loads, the oil must often function as a coolant. This method utilizes a solid jet of cool oil which is directed into the bearings. Here adequate drainage is especially important. The oil jets may be formed integrally with the outer preload spacer.
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L u b r i c a t i o n
o
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S
m
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B
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Examples of good modern practice in the lubrication of small bearings. These designs have the feature that no attention to lubrication is required over long periods. Several of them show applications of porous bronze bushings for long-life lubrication. Herbert Chase
Co py rig hte dM ate ria l
Spring wire
Bronze bushing-
Capillary space for oil
Sealing disk
Oil
"Rotors
So/aferec/ seam
Thtckplate Thin plate
Pinion 200rpm
This electric clock mechanism is inclosed in an oil-tight case with only a single opening for the 1-r.p.m. shaft. The bushing for this shaft projects sufficiently far into the case so that the oil level is below its inner end regardless of how the case is tilted. Oil feeds by capillary action between the places as indicated and works out along the shaft.
Porous metal
Spun over
Ia this design, the main plate H of the rotor tends, because of magnetic attraction, to stay in the same place. The central bronze bushing is a press fit in the main rotor plate and turns with it. On the outside of the bushing is a floating flywheel assembly made of the cupped stamping /, the pinion, and the sealing disk, the latter inclosing a series of chamois-skin washers that have been soaked in oil. Oil seeps slowly through holes in the bushing, and thus to the bearing surfaces.
AiT;
hole
Below, to the left is an oil resrevoir cast integrally; to the right, a drawn metal shell is screwed into the hub for an oil reservoir. In both designs, lubricant is fed through the porous metal bushing. Increased bearing temperature brings additional oil to the bearing surface because of expansion and increased oil fluidity.
Bushing Sapphire
disk
Brass washer
Chamois skin washers
Core
Po tor
Oil space
Rotation shaft
Pinion SOr.pm*
Bellows leather washer
The rotor shaft turns in a phosphor bronze bushing pressed into the stainless steel core of the motor. The oil seeps in minute quantities through the cylindrical porous plug, through the bellows leather washer, around the floating thrust jewel or sapphire disk, and finally into the bore of the bushing in which the rotor shaft turns. The bearing clearance is held within the limits of 0.0008 to 0.0003 in.
Copyright © 2005 by The McGraw-Hill Companies
Retrieved from: www.knovel.com
Co py rig hte dM ate ria l
Below are shown three different designs of bearings for extremely light duty, as in clocks and meters. To the left is a self-aligning bearing having a porous bushing seated in a two-piece cadmium-plated steel shell which also holds a felt washer saturated with sufficient oil to last a year or more in ordinary service. In the center is shown a design wherein a pressed steel frame forms a spherical seat for the porous bearing. A light stamping incloses an oil-soaked felt washer that contains sufficient lubrication for the H(e of the motor. To the right is shown the bearing for an electric clock, the light cupped stamping that contains the oil-soaked felt being pressed over the bearing flange. Jn both of these designs, the lubricant in the felt is sufficient for the life of the motor.
A cup-shaped stamping (below) holds the oil-soaked felt in the housing, and also acts as a dust shield. Lubrication of the bearing is through the porous bushing which is die-pressed from powdered metal. The lubricant is always fed to the outer wall of the bushing, which acts as a wick. To the right is shown an optional construction wherein an annular groove in the bearing housing forms the oil reservoir.
0/7 hole
In this design, an annular groove for oil or light grease is cored in the housing of the bearing. As indicated, oil-soaked wool waste can be packed in the cored recess. The concentric grooves at each end of the porous bushing are for the purpose of catching any end leakage. A refinement would be the addition of drilled holes to lead the oil back to the cellar. The additional oiler at the bottom is optional.
O/'/er Opttonor/
optional
In this wick-feed arrangement for oil or grease, capillary action feeds the lubricant to the surface of the porous bushing. For light service, sufficient lubricant is contained in the cup to last over a long period of time. The addition of the oiler shown in the end view is for the purpose of convenience so that the machine user will be more apt to give some attention to lubrication. Note the metal dust shield.
Copyright © 2005 by The McGraw-Hill Companies
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C a g e i n
B
K e e p s
L i n e
a n d
B e a r i n g s L u b r i c a t e d
Co py rig hte dM ate ria l
all-to-ball friction in bearings generates heat, limits the speed, and shortens the life of linear-motion guides. To solve these problems, engineers at THK designed a caged-ball system that places recirculating bearings in a retainer, or cage, that separates and aligns the bearings. The cage creates a bearing chain with spaces, or grease pockets, to hold lubricant and keep Block the bearings from touching each other. Separating the bearings provides several benefits. Because the bearings are not in contact with one another, there is much less metallic noise during operation. The lack of bearing-to-bearing contact also decreases wear and allows room for lubricant, two factors which promote long-term, maintenance-free operation. Meanwhile, the lack of bearing noise or vibration means rolling resistance is more End plate uniform, keeping performance of the linear guide consistent. And End seal reduced heat levels and low bearing stresses lets the linear guide move at higher speeds. The caged-ball technology is especially Bait bearings . well suited for medical devices and semiconductorinspection applications, according to THK, and is available in a wide Grease pocket variety of linear-guide models.
Caged-balls
Courtesy: Machine Design: © Published by Penton Media, Inc. Copyright © 2005 by The McGraw-Hill Companies
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